The environment around the biggest nuclear power plant in Europe is “becoming increasingly unpredictable and potentially dangerous,” the head of the U.N. nuclear watchdog said on Saturday.

The Zaporizhzhia power plant in southeast Ukraine is facing “extremely real nuclear safety and security risk,” according to International Atomic Energy Agency Director-General Rafael Mariano Grossi.

The threat of a serious nuclear accident and its ensuing effects on the populace and the environment, he said, must be eliminated.

He added that the Russian occupied facility, which is almost twice the size of Chernobyl, “must be protected.”

“I’m extremely concerned about the very real nuclear safety and security risks facing the plant. We must act now to prevent the threat of a severe nuclear accident and its associated consequences for the population and the environment,” he said.

The statement said that the IAEA had received information that residents from the nearby town of Enerhodar, where most of the plant staff live, had started and the organization was “closely monitoring the situation for any potential impact on nuclear safety and security.”