Ukraine's military said Friday morning that Russian forces have captured a massive nuclear facility in southeastern Ukraine, after the nuclear plant was hit by artillery fire and set ablaze.

The Zaporizhzhia nuclear power plant in Ukraine, the largest of its kind in Europe, was on fire earlier after an attack by Russian troops, the mayor of the nearby town of Energodar, Dmytro Orlov said, according to Reuters.

There was fierce fighting between local forces and Russian troops, Orlov said in an online post, adding that there had been casualties without giving details.

Ukrainian authorities had earlier reported that Russian troops were stepping up efforts to seize the plant and had entered the town with tanks.

"As a result of continuous enemy shelling of buildings and units of the largest nuclear power plant in Europe, the Zaporizhzhia nuclear power plant is on fire," Orlov said on his Telegram channel, citing what he called a threat to world security.

Ukrainian Foreign Minister Dmytro Kuleba warned of a disaster should an explosion occur at the power plant.

“Russian army is firing from all sides upon Zaporizhzhia NPP, the largest nuclear power plant in Europe. Fire has already broke out. If it blows up, it will be 10 times larger than Chernobyl! Russians must IMMEDIATELY cease the fire, allow firefighters, establish a security zone!” he tweeted.

Ukraine's Ministry of Energy initially said that Ukrainian firefighters could not begin efforts to extinguish the flames at the nuclear reactor due to gunfire from Russian troops, but it was later reported that the firefighters were permitted to enter the compound.

Hours later, Ukrainian authorities reported that firefighters had extinguished the blaze.

"We demand that they stop the heavy weapons fire," Andriy Tuz, spokesperson for the plant in Enerhodar, said in a video posted on Telegram. "There is a real threat of nuclear danger in the biggest atomic energy station in Europe."

US President Joe Biden spoke with Ukrainian President Volodymyr Zelensky to receive an update on the fire at the Zaporizhzhia nuclear power plant in Ukraine, the White House said in a statement.

Biden joined Zelensky "in urging Russia to cease its military activities in the area and allow firefighters and emergency responders to access the site," the statement said.

Earlier this week, the International Atomic Energy Agency’s (IAEA) 35-nation Board of Governors held an emergency meeting over the war in Ukraine and the threat to nuclear waste facilities in the country.

The incident at Zaporizhzhia came hours after IAEA chief Rafael Grossi called on Russian and Ukrainian troops not to fight in the area.

"Director General Grossi appealed for an immediate halt to the use of force at Enerhodar and called on the military forces operating there to refrain from violence near the nuclear power plant," the IAEA said in a statement.

Russian forces last week seized the spent nuclear fuel and radioactive waste facilities at Chernobyl, the site of the world's worst nuclear accident at a now-defunct power plant.

The takeover prompted condemnation from the United States, after “credible” reports were received that Russian soldiers are holding staff of Chernobyl hostage.