A Ukrainian drone crashed into a nuclear waste storage facility at the Kursk power plant in western Russia, damaging its walls, Russia's foreign ministry said, calling on other governments to condemn Kyiv.
Ukraine must have known that its actions could have caused a full-scale nuclear catastrophe, the ministry's statement said.
"We call on all governments to issue a strong condemnation of Kyiv's barbaric actions, which are extremely dangerous and could lead to irreparable consequences," said ministry spokeswoman Maria Zakharova.
Moscow said on Friday that it had thwarted the drone attack, and two news outlets said an explosion had damaged the facade of a warehouse storing nuclear waste.
Zakharova said one explosive-packed drone had damaged the nuclear waste facility's walls while another two had hit an administrative building complex.
"According to preliminary data, the drones used in the attack on the nuclear power plant used components supplied by Western countries," she said, adding that such an attack must have had the permission or possibly of Ukraine's allies or perhaps been ordered by them.
The Kursk plant said after the attack that there were no casualties and that radiation levels and operations were normal.
Ukraine generally declines to confirm or deny military operations inside Russian territory.
Thursday night's incident came a day after Ukrainian President Volodymyr Zelenskiy said a Russian drone attack in Ukraine's western Khmelnitskyi region had probably targeted the area's nuclear power station.
The UN nuclear watchdog said the attack destroyed "numerous windows" at the site but did not affect the Ukrainian plant's operations or connection to the electricity grid.
Reuters was unable to confirm either incident independently.