The U.N. chief discusses nuclear safety concerns at Zaporizhzhia with Russia’s defense minister.

The United Nations’ secretary general has spoken with Russia’s defense minister about the threat of a meltdown after days of shelling at a Ukrainian nuclear power plant, according to the United Nations. It also said it could help send in nuclear inspectors if both of the warring sides agreed.

Daily shelling at the complex, the Zaporizhzhia Nuclear Power Plant, which is occupied by Russian forces and operated by Ukrainian workers, has made it the first active nuclear power plant known to be at the center of fighting. It is Europe’s largest nuclear power plant.

In a telephone call on Monday, the two officials — António Guterres, the U.N. secretary general, and Sergei K. Shoigu, the Russian defense minister — discussed “conditions for the safe operation” of the complex, Russia’s Defense Ministry said in a post on the Telegram social media app. They also discussed a deadly July explosion at the Olenivka prisoner camp.

On Tuesday President Emmanuel Macron of France and President Volodymyr Zelensky of Ukraine spoke by telephone about safety threats at the Zaporizhzhia plant. According to a statement from Mr. Macron’s office, the French president stressed his concern about the “ongoing clashes on the safety and security of Ukrainian nuclear facilities” and called for the withdrawal of Russian forces.

It remains unclear who is to blame for the attacks at the Zaporizhzhia plant. The Ukrainians have accused the Russians of directing strikes there to cut off energy supplies to other cities and to try to discredit the Ukrainian military in the world’s eyes. The Russians say Ukraine is doing the shelling.

The officials’ phone call came on the same day that the Ukrainian company that oversees the nation’s nuclear plants said that Russian forces had in the past week targeted a nearby fire station that is responsible for extinguishing blazes at the facility in the event of an emergency. That poses “a serious risk to the safe operation of the plant,” the company, Energoatom, said in a statement.

“There are still risks of hydrogen leakage and sputtering radioactive substances, and the risk of fire is high,” the statement said, adding that three of the radiation monitoring sensors around the plant had also been damaged by recent shelling.

It was impossible to independently evaluate that assessment.

Last week, Mr. Guterres urged Ukraine and Russia to allow international inspectors to visit the complex and called for an immediate stop of all military activity near the plant.

Stéphane Dujarric, a spokesman for the secretary general’s office, said in a statement that the organization had the “logistics and security capacity” to support a visit from the International Atomic Energy Agency to the Zaporizhzhia plant, “should both Russia and Ukraine agree.”

Russia has expressed support for such a visit, but Ukraine’s government has not officially endorsed it, possibly out of concern that it could somehow legitimize Russia’s occupation of the nuclear plant.

The head of the local military administration, Oleksandr Starukh, said on Tuesday that radiation levels at the plant remained “stable,” but he noted that the situation could change quickly.

He said an evacuation plan for the region around the nuclear power plant and for the radiation contamination risk zone was being adjusted to take the fighting into account.

“The situation is dangerous not only for the Zaporizhzhia region,” he said in an interview on Ukrainian television, adding that a mandatory evacuation zone in the case of an accident would include more than 400,000 people in the region and in a neighboring one.

Marc Santora and Constant Méheut contributed reporting.