A fire at the Zaporizhzhya nuclear power plant in the eastern Ukrainian city of Enerhodar was extinguished Friday, according to Ukraine’s State Emergency Service.

The fire occurred in a training building at the site after shelling from Russian forces. There were no victims, the emergency service said.

The Zaporizhzhia nuclear power plant is the largest in Europe.

Meanwhile, Energodar Mayor Dmytro Orlov told reporters Friday morning that the city is now under the control of Russian forces and fighting near the Zaporizhzhya nuclear power plant has stopped. It's the second Ukrainian nuclear facility to fall under Russian control since the invasion began Feb. 24. Last week, Russian forces seized the Chernobyl nuclear power plant, where the world's worst nuclear accident took place in 1986, and the surrounding exclusion zone, which includes the ghost city of Pripyat.

Ukraine's national nuclear regulator has said that the Zaporizhzhia nuclear power plant's employees are being permitted to work as normal, safety systems are currently functioning and there was no reported change in radiation levels at the site.

-ABC News’ Brian Hartman and Patrick Reevell

The International Atomic Energy Agency (IAEA) has appealed for a halt of the use of force at Ukraine's largest nuclear power plant and warned of "severe danger if any reactors were hit."

The United Nations nuclear watchdog said in a statement early Friday that it was informed by Ukraine that the Zaporizhzhia nuclear power plant, the largest in Europe, had been shelled overnight in the eastern city of Enerhodar. IAEA Director-General Rafael Mariano Grossi "immediately" spoke with Ukrainian Prime Minister Denys Shmyhal as well as the country’s national nuclear regulator and operator about the "serious situation." Grossi is expected to hold a press conference later Friday.

According to IAEA, the Ukrainian regulatory authority said a fire at the site had not affected "essential" equipment and plant personnel were taking mitigatory actions, and that there was no reported change in radiation levels at the plant.

Ukraine's State Emergency Service said the blaze, which occurred in a training building after shelling from Russian forces, was extinguished Friday morning.

The IAEA said it is putting its Incident and Emergency Center (IEC) in "full response mode" due to the situation at the Zaporizhzhia nuclear power plant. The agency continues to closely monitor developments at the facility and remains in constant contact with Ukraine.

Ukrainian President Volodymyr Zelenskyy gave an urgent plea for intervention after officials said Russian troops shelled Ukraine's largest nuclear power plant overnight.

"Russia wants to repeat Chernobyl, but six times worse," Zelenskyy said in a video message. "Europe wake up, tell your politicians: 'Russian troops are shelling a nuclear power plant in Ukraine. Zaporizhzhya nuclear power plant.'"

The president warned there are six power units at the Zaporizhzhia nuclear power plant -- where a fire ignited during the shelling -- and only one power unit exploded at the Chernobyl nuclear power plant, the site of the 1986 nuclear disaster.

"The Russian military must be stopped immediately," Zelenskyy said. "Shout to your politicians. Ukraine has 15 nuclear units. If there is an explosion, it is the end of everything. The end of Europe. This is the evacuation of Europe. Only immediate action by Europe can stop Russian troops. Prevent the death of Europe from the catastrophe at the nuclear power plant."

President Joe Biden spoke with Zelenskyy to receive an update on the fire at the power plant and "joined President Zelenskyy in urging Russia to cease its military activities in the area and allow firefighters and emergency responders to access the site," the White House said in a readout of the call.

British Prime Minister Boris Johnson also spoke to Zelenskyy about the "gravely concerning situation" at the power station and said he would be seeking an emergency U.N. Security Council meeting "in the coming hours," his office said.

A White House official told ABC News its latest information shows no indications of elevated levels of radiation.

The International Atomic Energy Agency, the United Nations nuclear watchdog group, also tweeted that Ukraine's regulatory authority said there hasn't been any change in radiation levels reported at the site in the wake of the blasts.

-ABC News' Uliana Lototska and Molly Nagle

Russian troops are firing at Ukraine's largest nuclear power plant, officials said.

"Russian army is firing from all sides upon Zaporizhzhia NPP, the largest nuclear power plant in Europe," Ukrainian Minister of Foreign Affairs Dmytro Kuleba tweeted early Friday. "Fire has already broke out. If it blows up, it will be 10 times larger than Chornobyl! Russians must IMMEDIATELY cease the fire, allow firefighters, establish a security zone!"

Andriy Tuz, a spokesperson for the power plant, warned in videos posted to Telegram that Russian shelling caused a fire at the plant. He said the first power unit was hit and that rescuers have not yet been able to put out the fire due to the ongoing shelling.

The International Atomic Energy Agency, the United Nations nuclear watchdog group, said only Unit 4 was in operation currently and "radiation levels and fire safety at the NPP is within the norm." The fire broke out at a training building outside the power plant, the IAEA said.

The power plant's livestream captured blasts and a fire at the facility.

The situation at Ukraine's largest nuclear power plant has become "critical," authorities had warned earlier Thursday as Russian troops approached the site.

"The battle is going on in the town of Enerhodar and on the road to the ZNPP (Zaporizhzhia Nuclear Power Plant) site," Ukraine's regulatory authority said in an "urgent letter" to the IAEA.

Ukraine reported that Russian tanks and infantry “broke through the block-post” to the town of Enerhodar, near the power plant, according to IAEA Director General Rafael Mariano Grossi, who called on troops to refrain from use of force.

During an emergency IAEA board of governors meeting this week, Grossi warned that an incident affecting nuclear facilities "could have severe consequences, aggravating human suffering and causing environmental harm" beyond Ukraine's borders.

IAEA tweeted it is aware of reports of shelling at the power plant and is in contact with Ukrainian authorities.

-ABC News' Cindy Smith, Kirit Radia and Bill Hutchinson

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler