In a statement, Energoatom said it believed Russia, which controls the power plant in southern Ukraine, was preparing to conduct a “large-scale provocation” there. Moscow itself accused Kyiv of preparing a “provocation” at the site on Thursday.

“There is information that the Russian occupation forces are planning to shut down the power blocks and disconnect them from the power supply lines to the Ukrainian power system in the near future,” the Ukrainian statement said.

“The Russian military is currently looking for fuel suppliers for the diesel generators, which are supposed to turn on after the power units are shut down in the absence of an external power supply for the nuclear fuel cooling systems,” it said.

The vast nuclear power plant, Europe’s largest, was captured by Russian forces in March, but it is still staffed by Ukrainian technicians, though only two of its six reactors are working at full capacity.

Turning the plant off would pile new pressure on Ukrainian supplies, particularly in the south. Ukraine is already bracing for its most difficult winter since independence and preparing for a possible energy shortage.

(Reporting by Max Hunder; writing by Tom Balmforth; editing by Nick Macfie)