The catastrophic collapse of a dam in southern Ukraine has made Kyiv worried that Russia might stage an attack on the Zaporizhzhia nuclear plant to foment panic and quell Ukrainian advances on the frontline, Ukraine’s energy minister said Monday.

Herman Halushchenko said the destruction of the dam while under Russian control in the Kherson region proved “there are no red lines” for Moscow. He said it warrants the level of alarm Ukraine’s leadership has been raising in recent weeks of an alleged Russian ploy to attack the nuclear plant in a possible false flag operation.

Ukrainian President Volodymyr Zelenskyy alleged last week, citing intelligence reports, that Russian troops placed “objects resembling explosives” atop several power units to “simulate” an attack. Drone and satellite images obtained by the Associated Press showed unidentified white objects on the roof of the plant’s fourth power unit, but Ukrainian leaders have so far been unable to provide further evidence.

While Russia accuses Ukraine of bombarding the Kakhovka dam, Kyiv blames Moscow for the attack on the dam in late May, which triggered a humanitarian crisis and caused widespread ecological devastation. An AP investigation found that Moscow had the means and motive to carry out the attack.

Halushchenko said he and Zelenskyy had raised alarms as early as October 2022 that the Russians could plant mines to blow up the Kakhovka dam.

“For many many people it sounded ridiculous … and when it happened everybody understood that there are no red lines for them,” he said in a sit-down interview with The Associated Press. “And of course it’s all connected to the counter-offensive operation, and after Kakhovka, the one tool which they still have is Zaporizhzhia.”

Nuclear Plant Seized by Russia in 2022

The nuclear plant was seized by Russia in March 2022, in the first weeks of the war in Ukraine, raising fears of a nuclear accident. Over the past year, Russia and Ukraine repeatedly accused each other of shelling the plant.

Ukraine’s military intelligence has claimed for weeks, without providing evidence, that Russia is planning a “large-scale provocation” at the nuclear power plant, Europe’s largest, in the southeast of the country.

Around the same time, Ukraine launched the early phase of its much anticipated counter-offensive last month and has reported steady advances along multiple directions of the 1,500 kilometer (930-mile) frontline. An incident at the plant could halt Ukraine’s advance, Zelenskyy has said.

Ukrainian military intelligence reports have said that Russia placed mines on the roof of the nuclear plant, and put remote-controlled and regular anti-personnel mines in technical and machine rooms.

Image experts the AP spoke to could not identify the objects that have been seen on the roof.

Jeffrey Lewis, a professor at the Middlebury Institute and satellite image expert, said the objects appeared to be placed on the roof of the unit’s turbine hall, and, if it turns out to be a bomb, is unlikely to cause serious damage to the reactor.

The Russians have cited security concerns in granting only limited access to officials from the International Atomic Atomic Energy Agency. The agency’s Director General Rafael Mariano Grossi said recently that the IAEA had recently gained access to more of the site, including the cooling pond and fuel storage areas.

The Ukrainians had said those areas were mined by the Russians, but the IAEA found they were not, Grossi said. The agency has not yet been given access to inspect the roof of the plant.

Haluschenko noted that the IAEA representatives were not able to access the entire site. “So the Russians allowed them to see only what they decided they could see, and that is the problem,” he said.