CNN  — 

Ukraine’s Zaporizhzhia nuclear power plant, which is currently held by Russian forces, has been reconnected to Ukraine’s electricity grid, the country’s nuclear operator said in an updated statement on Friday, a day after the plant was disconnected for the first time in its history.

The statement from Energoatom said that at 2.04 p.m. local time on Friday one of two reactors “that was stopped yesterday was connected to the power grid, and capacity is being added.”

In a later statement, the operator said a second reactor had been connected. “Despite numerous provocations by the (Russian) occupiers, [Zaporizhzhia plant] continues to work in the energy system of Ukraine and provide our country’s electricity needs,” Energoatom said in a statement.

Ukrainian President Volodymyr Zelensky congratulated plant’s workers on Friday for protecting it “from the worst-case scenario, which is constantly being provoked by Russian forces,” he said during a daily address. “Currently, the station is connected to the network. Congratulations! It produces energy for Ukraine.”

Fires at a nearby thermal power plant had caused the last remaining electricity power line, which powers the station, to disconnect twice on Thursday, according the nuclear operator at the time. The plant’s three other lines had been “lost earlier during the conflict” it added.

The power supply was restored later on Thursday, but Zaporizhzhia nuclear power plant remained disconnected from the country’s power grid until Friday. The two nuclear reactors which remain operational at the plant need an electricity source in order to function and feed power into the grid.

The nuclear plant, which is Europe’s largest, has been under Russian control since March. Clashes around the complex have sparked widespread concern and fears of a disaster.

Kyiv has repeatedly accused Russian forces of storing heavy weaponry inside the complex and using it as cover to launch attacks, knowing that Ukraine can’t return fire without risking hitting one of the plant’s six reactors.

Moscow, meanwhile, has claimed Ukrainian troops are targeting the site. Both sides have tried to point the finger at the other for threatening nuclear terrorism.

On Thursday, Zelensky said backup diesel generators were “immediately activated” at the plant to avert a “radiation disaster.”

“The world must understand what a threat this is: If the diesel generators hadn’t turned on, if the automation and our staff of the plant had not reacted after the blackout, then we would already be forced to overcome the consequences of the radiation accident,” Zelensky said during his nightly address.

The generators are installed to supply power to cooling pumps to stop the fuel from overheating in the event of an electricity outage.

Kyiv has repeatedly accused Russian forces of storing heavy weaponry inside the complex and using it as cover to launch attacks.

On Friday, Zelensky also emphasized that “the situation (at the plant) remains very risky and dangerous. Any repeat of yesterday’s events, that is, any disconnection of the plant from the grid, any actions by Russia that could trigger the shutdown of the reactors, will again put the plant one step away from disaster.”

He stressed that officials from the IAEA, the UN’s nuclear watchdog, must be given urgent access to the site.

An administrative worker at the plant told CNN Friday that amid “shelling around the station and the city, smoke from fires, dust from the ash dump of a thermal power plant,” the “situation sometimes looks like the end of the world.”

“It’s really tough when there are strong winds,” the worker, who has spoken with CNN on previous occasions and whose identity is not being disclosed for their security, added.

Zaporizhzhia nuclear power plant generates about 20% of Ukraine’s electricity and a prolonged disconnection from the national grid would have been a huge challenge for Ukraine as colder weather approaches.

Russia on Friday said it was doing everything possible to make sure a team from the International Atomic Energy Agency (IAEA) could access the nuclear power plant, Foreign Ministry Spokeswoman Maria Zakharova said in a statement.

The plant is located in the Russian-occupied part of southern Ukraine. The IAEA has said it has not been able to visit the facility since before the conflict began six months ago.

CNN’s Pierre Meilhan, Uliana Pavlova and Petro Zadorozhnyy contributed to this report