Fighting has erupted on the grounds of Ukraine’s Zaporizhzhia nuclear power plant – the largest of its kind in Europe – with Kiev accusing Russian forces of setting fire to a building on the site with artillery blasts before they seized the facility. Radiation in the area remains at normal levels, officials say.

Citing Ukrainian authorities, the UN’s International Atomic Energy Agency (IAEA) issued a press release on Thursday noting that Russian tanks and infantry had broken through a line of defense outside the town of Enerhodar, which encompasses the nuclear site, and were advancing on the plant. Earlier this week, Russia informed the nuclear watchdog that it had taken control of the area surrounding the facility. 

Unverified footage circulating online purported to show the attack in progress, and was relayed by major US media networks including CNBC’s Shepard Smith. NPR also cited security video from the plant, claiming it showed “what appear to be Russian troops” at its gate.

BREAKING: Europe’s largest nuclear power plant in southern #Ukraine is reportedly being shelled by Russian troops right now. Watch ⬇️ pic.twitter.com/HGklnjOuQL

— The News with Shepard Smith (@thenewsoncnbc) March 4, 2022

Ukraine’s Foreign Minister Dmytro Kuleba said Russia had attacked the power plant “from all sides” and called for an immediate end to the fighting, warning that if the nuclear station “blows up,” it would be “10 times larger than Chernobyl.”

Enerhodar Mayor Dmitry Orlov said in a Telegram post that the plant was “on fire” due to “continuous enemy shelling,” but provided no other details about the status of the nuclear site, according to Reuters. An unnamed Ukrainian official also reportedly told US Senator Marco Rubio (R-Florida) that one reactor was “hit” and rendered “inactive with fuel inside,” but also declined to elaborate. The official did state that a meltdown was “unlikely,” however.

The Ukrainian State Emergency Service, meanwhile, issued an update confirming that a fire had erupted in a “training building outside the [nuclear power plant],” suggesting it posed no threat to its six reactors. However, the service said the facility is experiencing technical issues and that some systems remain disconnected. Ukraine’s energy regulator also told the IAEA that it observed “no change” in radiation levels at the plant, the UN agency said in a tweet, adding that the fire “has not affected ‘essential’ equipment.”

While officials denied any major damage, a spokesman for the power station, Andriy Tuz, claimed that one reactor caught fire during the attack, according to the Associated Press. He added that the reactor is currently under renovation, but still contains nuclear fuel. At least three of the facility’s reactors are now offline, per a New York Times report, though the reasons for each remain unclear.

Later on Thursday night, the White House said President Joe Biden held a call with his Ukrainian counterpart Volodymyr Zelensky and was updated on the situation at the plant. Energy Secretary Jennifer Granholm also said she was in touch with Kiev’s energy minister, adding that “We have seen no elevated radiation readings near the facility” and that its reactors “are protected by robust containment structures.”

UK Prime Minister Boris Johnson also consulted with Zelensky about the incident, Downing Street said.

By the early hours of Friday morning, Moscow had fully captured the station, with Energoatom – the state-owned enterprise that runs Ukraine’s four major power plants – confirming that there was “no further fighting, the fire was out, radiation was normal and Russian forces were in control.” Kiev’s emergency agency said there were no casualties in the clashes.

The Russian Defense Ministry later offered its own account of the skirmish, claiming the fire was a “monstrous provocation” by “a Ukrainian sabotage group.” It said its troops were ambushed from within the facility’s training complex in order “to provoke return fire,” and that the alleged saboteurs set fire to the building as they fled.

“Zelensky’s prompt statements about the alleged threat to the nuclear power plant and his talks with Washington and London leave no doubt. The purpose of the provocation of the Kiev regime at a nuclear facility is an attempt to accuse Russia of creating a source of radioactive contamination,” the ministry continued.

The Zaporizhzhia Nuclear Power Plant has come under assault in the past, long before Russia’s invasion last week. A gang of Ukrainian ultra-nationalist militants attacked the station in 2014 to expel “pro-Russian agitators” it claimed were at the site, but were disarmed by security. 

As fighting continues for major cities from Kiev to Kharkiv, Russian and Ukrainian negotiators met to discuss a possible ceasefire earlier on Thursday. The talks netted a limited deal, under which humanitarian corridors will be established to allow civilians to flee cities without interference by troops on either side. 

A direct communication line has also been established between the US European Command and the Russian military “for the purpose of preventing miscalculation, military incidents, and escalation,” an unnamed US official told the AP. It remains to be seen whether the new comms channel or ongoing bilateral talks between Kiev and Moscow will help to bring an end to the conflict, as discussions have reportedly made little progress so far.