Russia's President Vladimir Putin stands in front of the 6 meters long Tsar Pushka (Tsar Cannon), one of the Russian landmarks displayed in the Kremlin in Moscow, on July 31, 2014. A defiant Russia said yesterday that Western sanctions over Ukraine would backfire on the United States and lead to energy price hikes in Europe after Brussels and Washington unveiled the toughest punitive measures against Moscow since the Cold War.
Does Putin want war in Ukraine?
01:16 - Source: CNN

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NEW: Close to 1,400 people have been killed, and more than 4,000 wounded, since mid-April

"Today, with all certainty, there's a need to speak about a true war," says Russian official

A U.S. military team in Kiev is aiding the recovery effort of downed Flight MH17

NATO official says there are about 20,000 Russian troops near the Ukraine border

Donetsk, Ukraine CNN  — 

A new buildup of Russian troops along the Ukraine border raised concerns Tuesday that Moscow might be contemplating another intervention like the one that annexed Crimea earlier this year.

According to a NATO official, Russia now has about 20,000 troops stationed “in an area along the entire border with eastern Ukraine.” The buildup nearly doubled the troop deployment in the last week by adding 8,000 more forces to 12,000 already there, the official said.

It comes a week after the United States and the European Union increased economic sanctions on Russia for supporting pro-Russian separatists fighting Ukraine government forces in the eastern regions of Donetsk and Luhansk, along the border with Russia.

In addition, Russia’s Defense Ministry is staging a week of military exercises involving air troops and anti-missile defense forces. The exercises are taking place in Russia’s southern Astrakhan region, roughly 500 miles from the border with Ukraine.

Similar military exercises in the region preceded Russia’s annexation of Crimea in March, which escalated the Ukraine conflict following the ouster of pro-Moscow President Viktor Yanukovych a month earlier.

Donetsk braces for offensive

Meanwhile, Ukraine government security officials said Monday they were preparing for a “massive assault” on Donetsk city, state media reported. Inside the city, a rebel stronghold for months, shelling has already pushed some residents underground into cellars and half-built basements.

Russia’s Foreign Ministry claimed in a statement Monday that the Ukrainian military was firing missiles and using multiple rocket systems in and around the city.

It accused Ukraine’s government of wanting to continue the war and called for talks to find a political situation to the crisis.

With escalated fighting and Ukrainian forces making gains, the Russian deployment at the border could portend an intervention under the banner of a peacekeeping operation.

“On a human scale, the situation in the east – particularly in Donetsk and Luhansk – is disastrous. Today, with all certainty, there’s a need to speak about a true war,” Vitaly Churkin, Russia’s ambassador to the United Nations, said Tuesday.

Russian troop buildup

The NATO official said Russian forces gathering at the Ukraine border included a “spectrum” of assets: infantry, mechanized divisions, armor, a lot of artillery, conventional and air defense, and special forces and logistics.

“They are very capable Russian regular units and can move in a matter of hours and could significantly disrupt the situation” in eastern Ukraine, the official said.

The Ukrainian government and Western leaders accuse Russia of fomenting instability in its neighbor by arming and supporting the rebels there, which Russia denies.

The downing of Malaysia Airlines Flight 17 on July 17 exacerbated the situation.

Malaysian plane downed

U.S. and Ukrainian officials allege that a Russian-made missile shot down the plane from rebel-held territory, killing all 298 people on board. Russia and the rebel fighters deny involvement.

Earlier this year, Russia amassed about 40,000 troops on the Ukraine border and threatened to invade, NATO said in a fact sheet published last month.

Putin then ordered most of the soldiers to return to their bases, leaving about 12,000 of July 11, NATO said.

On Tuesday, Ukraine’s National Defense and Security Council said the Russian deployment now numbered as high as 45,000, and that there had been 26 clashes in the past 24 hours, including six attacks from Russian territory.

Meanwhile, Russian combat aircraft crew will practice firing at air and ground targets in unfamiliar territory, the defense ministry said of the military exercises in the region. The maneuvers will involve 100 aircraft, including fighter jets, bombers and combat helicopters.

In its fact sheet, NATO challenged Russian accusations that the alliance is escalating the crisis in Ukraine by bolstering its support for NATO members in Eastern Europe.

“Over the past months, Russia has also embarked on an unprecedented schedule of no-notice military exercises involving massive numbers of troops and heavy equipment,” NATO said, adding: “Russia should explain what its military plans are before it starts accusing others of posing a threat.”

Search for remains

An official with knowledge of the MH17 investigation told CNN