OR Russia accused Friday today Ukraine for an attempted attack on his nuclear power plant Kursk overnight, in what Russia’s foreign ministry described as an “act of nuclear terrorism”, days before the head of the International Atomic Energy Agency (IAEA) is expected to visit the region.

Fierce fighting is raging in the Kursk region of western Russia following the surprise cross-border attack launched by Kiev on August 6.

Ukraine’s Defense Ministry has not yet responded to a Reuters request for comment on this accusation, which is Moscow’s second in two days.

Earlier today TASS reported, citing an unnamed source, that a Ukrainian unmanned aerial vehicle (drone) attempted to attack the Kursk nuclear power plant during the night and specified that the drone was shot down near a spent nuclear fuel storage facility. Reuters was unable to independently confirm details of the alleged incident.

The Russian news agency then carried a statement from Russian Foreign Ministry spokeswoman Maria Zakharova, saying it constituted an “act of nuclear terrorism” that required an immediate response from the International Atomic Energy Agency.

IAEA chief Rafael Grossi is expected to visit the Kursk nuclear power plant next week. He has called for maximum restraint to avoid a nuclear accident.

Russian President Vladimir Putin had earlier on Thursday accused Ukraine of trying to attack the nuclear plant, noting that Moscow had informed the IAEA, without elaborating or citing evidence of a Ukrainian attack.

In Ukraine’s Aug. 6 blitzkrieg invasion of Kursk, Russia’s largest by a foreign force since World War II, thousands of Ukrainian troops crossed Russia’s western border, taking Moscow by surprise.

Fierce fighting is raging within about 30 kilometers of the nuclear plant as Russian forces battle to push back Ukrainian troops seeking to consolidate gains on the ground and expand the territory they have brought under their control.

The Kursk NPP has four reactors, two of which are operational. In 2018, the construction of two more reactors began.

The Russian state-owned nuclear power company Rosenergoatom announced today that unit no. 4 of the station will go offline on Sunday, August 25 for 59 days of “scheduled preventive maintenance.” The works will concern the modernization and extension of the operational life of the equipment.