Diplomats say the UN Security Council has scheduled an emergency meeting for March 4 following a fire at a nuclear power plant that Russian forces have seized in northeastern Ukraine that left atomic experts scrambling to monitor for radiation leaks.
The International Atomic Energy Agency (IAEA), Ukraine's nuclear agency, and nuclear officials from around the world said no leak had been detected from the Zaporizhzhya Nuclear Power Plant after responders finally put out the fire that burned out of control overnight after nearby shelling by invading Russian forces.
Local officials said Russian forces opened fire as their column approached Zaporizhzhya.
The incident prompted the UN and international atomic authorities to adopt emergency postures, and British Prime Minister Boris Johnson's office said he would request an emergency meeting of the UN Security Council to discuss the situation.
"Changes in the radiation situation have not been registered," Ukraine's State Nuclear Regulatory Inspectorate (SNRIU) said later.
WATCH: Staff at Ukrainian nuclear sites, Zaporizhzhya and Chernobyl are being held by Russian forces and working under the barrel of a gun, according to the former head of Ukraine's nuclear inspectorate.
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Ukrainian Nuclear Plant Staff 'Being Held,' Says Atomic Safety Expert
The nuclear plant at Zaporizhzhya, on the banks of a reservoir on the Dnieper River, is the largest in Europe and generates more than one-fifth of Ukraine's domestic electricity.
The IAEA said it was putting its incident and emergency center into full response mode due to the situation.
IAEA Director-General Raphael Grossi later said a "projectile" had struck an area that was "not part of the reactor" and described the situation as "normal operations." But he added that, "in fact, there is nothing normal about this."
Grossi praised the plant's Ukrainian staff for their bravery and resilience under "very difficult circumstances."
He said only one of six reactors was working, at around 60 percent capacity.
Video overnight showed a building, reportedly a training facility, burning at Zaporizhzhya.
Russian Defense Ministry spokesman Igor Konashenkov claimed, without evidence, that a Ukrainian "sabotage group" had set fire to the building.
But Zaporizhzhya Mayor Dmytro Orlov said Russian forces had opened fire on a checkpoint a few kilometers from the nuclear plant and civilians there and shelling pounded the area for at least an hour. He said the city had no water supply and power outages.
The regional administration in Zaporizhzhya later said Russian troops had seized the plant and "operational personnel are monitoring the condition of power units."
A protocol to the Geneva Convention restricts military attacks on nuclear facilities.
President Volodymyr Zelenskiy issued a video address after the fire began, urging Europeans to "please wake up. Tell your politicians -- Russian troops are shooting at a nuclear power plant in Ukraine."
Zelenskiy spoke with U.S. President Joe Biden and British Prime Minister Boris Johnson to update them about the situation at Zaporizhzhya.
Johnson's office said "the reckless actions of [Russian] President [Vladimir] Putin could now directly threaten the safety of all of Europe."