Grossi, in a statement on X, said Sunday that the three containment structures at the Zaporizhzhia plant, for the first time, had sustained three direct hits.

“This cannot happen,” Grossi wrote, saying it contravened five principles he set down in November 2022 to avoid a catastrophe at the plant.

Grossi said “no one can conceivably benefit or get any military or political advantage from attacks against nuclear facilities. This is a no go.”

Russia seized the plant soon after its February 2022 invasion of Ukraine. Shelling and artillery strikes have repeatedly hit close to the plant, at times cutting the electric lines maintaining its cooling operations. All six reactors have been shut down.

Ukraine has accused Russia of turning the plant into a military base for occupying troops, knowing Kyiv’s forces would be reluctant to strike it. Meanwhile, nearby residents have been living in fear of a potential radioactive disaster.

A statement on Sunday from the IAEA confirmed the physical impact of drone attacks on the plant, including one that hit a building housing one of the plant’s six reactors. The statement described this as “a serious incident” with the potential to “undermine integrity of the reactor’s containment system.” However, the agency reported that the drone strikes had not compromised nuclear safety.

Grossi appealed to military decision-makers “to abstain from any action violating the basic principles that protect nuclear facilities.”

The Kremlin spokesman, Dmitry Peskov, on Monday described the attacks as “a dangerous provocation.” In comments to reporters, Peskov accused Kyiv of “continuing its terrorist activity.”

Russia’s Investigative Committee, the country’s top law enforcement body, announced an investigation into the strikes on the plant.

Andriy Yusov, spokesman for Ukraine’s military intelligence agency, denied that Ukraine had attacked the plant. In comments to the Ukrainian Pravda newspaper, Yusov said Russia had previously mounted false-flag attacks on the plant.

Three employees at the plant were injured, according to the Investigative Committee.

“The Russian Investigative Committee will establish every detail of the incident and will identify the people behind this crime,” the agency said in a statement.

Rosatom, Russia’s nuclear agency, said on Sunday that the plant had experienced an unprecedented series of drone strikes, which directly jeopardized its safety.

The spokeswoman for Russia’s Foreign Ministry, Maria Zakharova, demanded that world leaders condemn what she called an “act of nuclear terrorism by the Kyiv regime” and accused the West of feeding “the monster [Ukrainian President Volodomyr] Zelensky.”

Yevgenia Yashina, a Russian-appointed spokeswoman for the plant, said the first drone hit a truck unloading food near its canteen. A second drone struck the cargo port area, and a third struck the dome on the building housing the sixth reactor, she said.

A second drone targeting the sixth reactor unit was shot down, Yashina said.

Dixon reported from Riga, Latvia. Natalia Abbakumova in Riga and Mary Ilyushina in Berlin contributed to this report.