Explosions have been seen and heard in parts of the Ukrainian capital Kyiv, as the fight by Ukrainian forces to hold back a Russian advance on the capital intensifies in the early hours of Saturday morning, amid warnings the city could fall within days and as officials handed out weapons to reservists. “This night will be very difficult, and the enemy will use all available forces to break the resistance of Ukrainians,” President Volodymyr Zelensky said in a late-night video message Friday. “This night we have to stand ground. The fate of Ukraine is being decided right now.” Earlier Saturday, videos from eyewitnesses showed explosions taking place in an area north-west of the Ukrainian capital Kyiv. There is a military base in the area. CNN teams in the capital also reported hearing loud explosions to the west and south of the city Saturday. Shortly afterward, Ukraine’s State Service of Special Communications said clashes are underway in an eastern suburb as well – as Russian forces close in on the capital from multiple sides. Meanwhile, the Ukrainian armed forces reported heavy fighting around the city of Vasylkiv, some 30 kilometers southwest of Kyiv. “Heavy fighting is currently underway in the town of Vasylkiv in the Kyiv region, where the occupiers are trying to land a landing party,” the armed forces said. Russian forces are close to Kyiv, Zelensky confirmed in his message Friday, advancing on the capital from the north and east after seizing control Thursday of an airbase just north of the city. But “Ukrainians resist the Russian aggression heroically,” he said. Russia’s military claimed earlier Friday its forces had staged a “successful landing operation” to capture Hostomel airfield, viewed as strategically important, on Kyiv’s outskirts. Zelensky’s comments came hours after a video was posted on his Facebook page, showing him with a group of men, saying, “We are here. We are in Kyiv. We are defending Ukraine.” Before dawn Friday, explosions lit up the sky above the capital as Russia targeted the city with missile strikes, according to a Ukrainian government adviser. A CNN team reported hearing two large blasts in central Kyiv and a third loud explosion in the distance, followed by at least three more explosions to the south-west of the city a few hours later. “Strikes on Kyiv with cruise or ballistic missiles continued,” Anton Gerashchenko, adviser to the Head of the Ministry of Internal Affairs of Ukraine told reporters via text message Friday. Meanwhile, the Ukrainian Defense Ministry said Russian reconnaissance troops had entered the Obolon district of northern Kyiv, just a few miles from the city center. Videos from the area showed chaotic scenes as civilians tried to hide from small arms fire. LIVE UPDATES ON INVASION A tweet from the ministry asked citizens of the district to report any suspicious movements, adding: “Make Molotov cocktails and take down the occupier.” CNN witnessed a group of Ukrainian security forces leave the city police headquarters with weapons and ammunition – apparently heading towards Obolon. Meanwhile, 92 people working at the Chernobyl power plant, the site of the world’s worst-ever nuclear disaster, have been taken hostage, the Ukrainian ambassador to the US said Friday. Russian forces took control of the site on Thursday, sparking fears that the fighting could interfere with the operation of nuclear waste facilities. As Russian troops advance, US intelligence officials are concerned that Kyiv could fall under Russian control within days, according to two sources familiar with the latest intelligence. However, the latest British defense intelligence assessment said Russia had made “limited progress” Friday in its attack. “Fighting continues in key locations. Russia has made limited progress so far today and Ukraine retains control of key cities. Ukrainian MOD reports that Russian forces have arrived in the suburbs of Kyiv,” the UK Ministry of Defence tweeted. A senior US defense official told reporters that the Russians have “about a third of their combat power” in Ukraine out of the total combat power they have amassed on the country’s borders right now, but “that does not mean that they will not commit more.” The Ukrainian Defense Ministry earlier said that airborne assault troops blew up a bridge over the Teteriv River at Ivankiv, about 30 miles north of Kyiv, successfully preventing a Russian column of forces from advancing towards the capital, which has a population of close to 3 million. For now, Ukraine’s democratically elected government remains intact but President Volodymr Zelensky warned in a video address late Thursday that “enemy sabotage groups” had entered this city and he is their No. 1 target. “They want to destroy Ukraine politically by destroying the head of state,” he said. “Russian forces continued to launch missile strikes on the territory of Ukraine. They say that they are only targeting military facilities, but these are lies. In fact, they do not distinguish in which areas they operate,” he said. “Such attacks on our capital haven’t occurred since 1941.” In an address Friday morning, Zelensky said Ukrainians were “showing their true heroism” but that they were defending their country “alone.” The sanctions imposed on Russia by Western powers are “not enough to get these foreign troops off our soil,” he said. A few hours later, Zelensky released a message in which he again called for Russian President Vladimir Putin to hold direct talks. “There is fighting all over Ukraine now. Let’s sit down at the negotiation table to stop the people’s deaths,” he said, speaking in Russian. Shortly afterward, Kremlin spokesman Dmitry Peskov said Russia was ready to send a delegation to Minsk, the capital of Belarus, for talks with Ukraine, Russian state news agency RIA-Novosti reported. “As you know, today the President of Ukraine Zelensky announced his readiness to discuss the neutral status of Ukraine,” Peskov said, according to RIA. The talks would concern “neutral status,” he suggested. Peskov said later Friday that the Ukrainian side had countered with a proposal to meet in Warsaw and then dropped contact. Zelensky has not directly proposed neutral status but has signaled a willingness to discuss it, while insisting his country be provided security guarantees. “Ukraine has been and remains ready to talk about a ceasefire and peace. This is our constant position,” Sergii Nykyforov, a spokesperson for Zelensky, said late Friday. He also denied what he called “claims that we have refused to negotiate.” Meanwhile, Putin called on Ukraine’s armed forces to overthrow their government in remarks to his security council Friday. “Do not let Banderites (Ukrainian nationalists) and neo-Nazis use your children, wives and old people as human shields,” Putin said in remarks aired on Russian state television. “Take power into your own hands, it looks like it will be easier for us to come to an agreement than with this gang of drug addicts and neo-Nazis that has settled in Kyiv and taken hostage the entire Ukrainian people.” Putin frequently repeats the baseless and inaccurate claim that the democratically elected Ukrainian government is a “Nazi” or “fascist” regime. The language has been roundly condemned internationally, especially considering that Zelensky is Jewish. Asked by CNN at a news conference Friday what Moscow’s plans were for the leadership of Ukraine as Russian forces advance on Kyiv, Russian Foreign Minister Sergey Lavrov replied: “Nobody is going to attack the people of Ukraine.” In an interview with CNN on the streets of Kyiv, former Ukrainian President Petro Poroshenko accused Putin of being “simply crazy” in wanting to “come here to kill Ukrainians” – and vowed they would resist. “We demonstrate a unique quality that we can stand against Russian aggression,” he said. Homes damaged The advance on Kyiv comes only a day after Russian forces entered Ukraine from three sides, by land, sea and air, prompting a barrage of international condemnation and sanctions – and questions about Putin’s wider ambitions for the country and its capital. It’s unclear how long Ukrainian forces can resist the advance of Russian forces who are much better equipped and have superior air power. Two residential buildings in Kyiv suffered damage in the early hours of Friday, but it’s not clear if they were intentionally struck or hit by debris, or if anyone was injured. Ukrainian Deputy Interior Minister Evgeny Yenin told CNN a Ukrainian Sukhoi Su-27 fighter jet was shot down over Kyiv. Photos tweeted by the emergency forces appear to show a fire at a two-story private house with debris from what looks to be a plane nearby. It is unclear if the house was hit by remnants of the jet. Separately, images showed firefighters working to put out a blaze at an apartment building on the left bank of the city. As they approach, many Ukrainians are preparing to fight back. Some 18,000 guns with ammunition have been distributed to reservists in the Kyiv region alone since the Russian invasion began early Thursday, Ukrainian Defense Minister Oleksiy Reznikov said, with more weapons on their way. Outside the Kyiv region, fighting continued in cities including Sumy, in the northeast, Chernihiv in the north and Kherson to the south. A CNN team that visited a bridge crossing from Russian-held areas into the southern city of Kherson saw four large shell craters, 10 discarded Ukrainian armored vehicles and several bodies, but the Ukrainians appeared to have been able to push Russian forces back. Low-flying jets could be seen overhead and air raid sirens wailed across the city. A Russian defense ministry spokesperson said in a statement that a “counter-offensive” was underway in Ukraine’s eastern Donbas region, and that Ukrainian service members had surrendered to Russian troops and pro-Russian separatists. CNN could not immediately check the veracity of those claims. Makeshift bunkers Officials in the country believe Russia’s plan is to overthrow the Ukrainian leadership and install a pro-Russian government. Those fears were shared with US Secretary of State Anthony Blinken, who said Thursday that he’s “convinced” Moscow is going to try to overthrow the Ukrainian government. If that happens, Blinken said he believes “Moscow has developed plans to inflict widespread human rights abuses – and potentially worse – on the Ukrainian people.” The fighting in Ukraine appears to be some of the worst conventional warfare Europe has seen since World War II and the conflicts in the Balkans in the 1990s. Preliminary figures indicate 137 Ukrainian solders have been killed, including every soldier defending an island in the Black Sea that was taken over by Russian troops, according to President Zelensky. The Ukrainian Defense Ministry said its armed forces had caused around 800 casualties among Russian forces since the attacks started early on Thursday. It was not immediately clear whether the ministry was referring solely to the number killed and CNN is not able to independently verify Ukraine’s figures. By the end of Thursday, Putin’s forces had launched “in total more than 160 missiles for airstrikes,” a senior US defense official said, prompting a response reminiscent of the late 1930s, with vulnerable children evacuated by train from eastern Ukraine and packed subway stations turned into makeshift bunkers as air raid sirens wailed. In an ominous sign a ground war could escalate, Zelensky barred male citizens between the ages of 18 and 60 from leaving the country, according to the State Border Guard Service. Zelensky also ordered a general military mobilization “in order to ensure the defense of the state, maintaining combat and mobilization readiness of the Armed Forces of Ukraine and other military formations, in a declaration signed late Thursday. More than 100,000 people have already fled areas most at risk of attack within Ukraine, according to the United Nations refugee agency. The mass movement followed warnings from the US Ambassador to the UN, who said Russia’s actions in Ukraine could create one of the largest refugee crises facing the world today, displacing as many as five million people. Polish officials reported an increase in the number of people crossing into the country from Ukraine in the hours after the Russian invasion began. Sanctioning Putin The United States will impose sanctions on Putin and Lavrov, White House press secretary Jen Psaki said on Friday, hours after the European Union and United Kingdom said they would do the same. The EU also announced a slew of other new sanctions on Russia, designed to have “maximum impact on the Russian economy and political elite.” European Commission President Ursula von der Leyen said the sanctions would hit Russia’s financial, energy and transport sectors, visa policy, and include export controls and export financing bans. “We want to financially isolate Russia, we want to cut all the ties between Russia and the international financial system,” said French Finance Minister Bruno Le Maire. Speaking in Brussels on Thursday, NATO Secretary-General Jens Stoltenberg described Russia’s attack on Ukraine as a “brutal act of war.” The alliance activated the NATO Response Force (NRF) for the first time ever in response to the invasion. The NRF is made up of land, air, sea and special operations forces from the allies that can deploy quickly in support of the NATO alliance. “We have over 100 jets at high alert, operating in over 30 different locations, and over 120 ships from the high north, to the Mediterranean. We activated the defense plans yesterday, and now elements of this force are being deployed,” Stoltenberg said during a press briefing on Friday, following an extraordinary meeting of NATO Heads of State and Government in Brussels. He also clarified that while the United States, Canada and European allies have “deployed thousands more troops” to the eastern part of the alliance, NATO is not deploying the entire Response Force. A big concern for NATO is whether Putin’s intentions lie beyond Ukraine, a prospect that risks drawing all 30 members – including the US, the United Kingdom, Canada, France and Germany – into a wider conflict on European soil. “You don’t need intelligence to tell you that that’s exactly what President Putin wants. He has made clear he’d like to reconstitute the Soviet Empire, short of that he’d like to reassert a sphere of influence around the neighboring countries that were once part of the Soviet bloc,” said Blinken on CBS Evening News. Blinken said NATO would stand in the way if those were Putin’s ultimate goals. “Now, when it comes to a threat beyond Ukraine’s borders. There’s something very powerful standing in his way. That’s article five of NATO, an attack on one is an attack on all,” the top diplomat said. On Thursday, the US Secretary of Defense ordered the deployment of 7,000 US service members to Europe. The deployment brings the number of US troops moved towards eastern Europe at more than 14,000.