"Three strikes were recorded on the site of the plant, near one of the power blocks where the nuclear reactor is located," Energoatom, Ukraine's state-run operator of the country's nuclear power plants, said in a statement.

"There are risks of hydrogen leakage and radioactive spraying. The fire danger is high," it said, adding that initially there were no casualties.

The global nuclear watchdog IAEA has been trying for weeks to send a team to inspect the plant. Ukraine has so far rejected the efforts, which it says would legitimise Russia's occupation of the site in the eyes of the international community.

The Zaporizhzhia plant in southeast Ukraine is the largest in Europe. Russian troops took control of it in March after the invasion began in late February.

On Monday, US Secretary of State Antony Blinken accused Moscow of using the plant as a "military base to fire at Ukrainians, knowing that they can't and won't shoot back because they might accidentally strike a nuclear... reactor or highly radioactive waste in storage".