It is the largest nuclear power plant in Europe and was occupied by Russia early in its invasion. Kyiv and Moscow blamed each other for attacks on the plant last week.

"The Russian military present at the Zaporizhzhia nuclear power plant are implementing the program of (Russian operator) Rosatom aimed at connecting the plant to the Crimean electricity grid," Energoatom president Petro Kotin told Ukrainian television.

"To do this, you must first damage the power lines of the plant connected to the Ukrainian energy system. From August 7 to 9, the Russians have already damaged three power lines. At the moment, the plant is operating with only one production line, which is an extremely dangerous way of working," he added.

"When the last production line is disconnected, the plant will be powered by generators running on diesel. Everything will then depend on their reliability and fuel stocks," Kotin warned.

Located not far from the Crimean peninsula, the plant has six of Ukraine's 15 reactors, capable of supplying power for four million homes.

Ukrainian President Volodymyr Zelensky on Monday raised the spectre of nuclear disaster after strikes on the plant.

And UN Secretary-General Antonio Guterres warned that any attack on a nuclear plant would be "suicidal".

"I hope that those attacks will end, and at the same time I hope that the IAEA will be able to access the plant," he said Monday.

Recent fighting around the plant has prompted the UN nuclear watchdog International Atomic Energy Agency (IAEA) to warn of the "very real risk of a nuclear disaster".