“The territory of the Zaporozhye nuclear power plant is occupied by the armed forces of the Russian Federation,” the Ukrainian nuclear inspectorate was quoted as saying by news agency AFP. The statement said plant staff were continuing to operate the reactor and supply power according to normal safety rules.

The Zaporizhzhia power plant had caught fire as it came under shelling from Russian forces. Though the fire was later extinguished, the incident sparked concerns that radiation could leak from the damaged power station.

US Energy Secretary Jennifer Granholm said the reactors at Zaporizhzhia nuclear power station “are protected by robust containment structures and reactors are being safely shut down”. Ms Granholm tweeted she had just spoken with Ukraine’s energy minister about the situation at the plant. “We have seen no elevated radiation readings near the facility,” Ms Granholm said.

Ukraine’s President Volodymyr Zelensky accused Moscow of trying to “repeat” the Chernobyl nuclear disaster and said he had spoken with international leaders including US President Joe Biden about the crisis at the Zaporizhzhia nuclear plant.

Images on a live feed from the site earlier showed blasts lighting up the night sky and sending up plumes of smoke, with the International Atomic Energy Agency urging an immediate halt to fighting there. “No country other than Russia has ever fired on nuclear power units,” Mr Zelensky said in a video message.

“This is the first time in our history. In the history of mankind. The terrorist state now resorted to nuclear terror. If there is an explosion, it is the end of everything. The end of Europe. This is the evacuation of Europe. Only immediate European action can stop Russian troops,” Mr Zelensky said as he appealed for global help.

British Prime Minister Boris Johnson accused Russian President Vladimir Putin of endangering all of Europe Friday, after the attack on the nuclear power plant. “The Prime Minister said the reckless actions of President Putin could now directly threaten the safety of all of Europe,” according to a Downing Street statement.

The station at Zaporizhzhia, an industrial city in southeast Ukraine, supplies an estimated 40 per cent of the country’s nuclear power and, according to Mr Zelensky, houses six of Ukraine’s 15 reactors.

Ukraine’s nuclear facilities have been a main point of concern after Russia’s military invaded the country last week and began bombarding cities with shells and missiles.

A nuclear power plant disaster in Ukraine’s Chernobyl in April 1986 was one of the worst disasters in the history of nuclear power generation. Mistakes by engineers and compounded by other factors led to an uncontrolled chain reaction that resulted in several massive explosions in Chernobyl in 1986.