A nuclear power plant twice the size of Chernobyl has been shelled, sparking fears of a ‘catastrophe’

Russia has denied shelling the plant, instead accusing Ukraine’s 44th Artillery Brigade of launching attacks from the nearby town of Marganets. Ukraine was responsible for “a new act of nuclear terrorism,” the Russian Defense Ministry said in a statement, according to the state-owned RIA Novosti news agency.

The nuclear reactor complex was operating in “normal mode,” Yevgeniy Balitsky, the Russian-installed head of the local administration, said Monday, according to the Russian news agency Interfax. Later, the Defense Ministry said the high-voltage line had been damaged, causing a power surge and forcing staff members to reduce output from two of the site’s six reactors to “prevent disruption.”

Kremlin spokesman Dmitry Peskov said the shelling was “extremely dangerous” in his daily call with reporters Monday, adding, “We expect the countries that have absolute influence on the Ukrainian leadership to use this influence in order to rule out the continuation of such shelling.”

U.S. Secretary of State Antony Blinken said last week that he was “deeply concerned” by Russian forces’ takeover of the plant.

“There are credible reports,” he said, “that Russia is using this plant as the equivalent of a human shield, but a nuclear shield in the sense that it’s firing on Ukrainians from around the plant, and of course the Ukrainians cannot and will not fire back lest there be a terrible accident involving a nuclear plant.”

Russian forces seized the plant in March, just over a week after the invasion began, but it is still run by its Ukrainian staff. Around 500 Russian soldiers and 50 military vehicles are at the plant, Energoatom said.

The 1986 disaster at the Chernobyl nuclear power plant near the northern Ukrainian city of Pripyat is considered the worst on record. It required the evacuation of more than 100,000 people living within nearly 19 miles, and the resulting radiation was detected across Europe. Officially, fewer than 50 people died as a direct result of Chernobyl, a figure that scientists and environmental groups vigorously contest.

Ukrainian lawmakers have speculated that as many as 3 million people could die and that 51 million more could be otherwise affected by radiation in a serious incident involving the Zaporizhzhia plant.

Josh Lederman reported from Kyiv, and Patrick Smith reported from London.

Patrick Smith is a London-based editor and reporter for NBC News Digital.