ZAPORIZHZHIA, Ukraine — The United Nations’ atomic energy chief warned President Zelensky in a meeting Monday that the perilous situation at Europe’s largest nuclear plant “isn’t getting any better” as relentless fighting in the area puts the facility at risk of a nuclear disaster.

The Zaporizhzhia plant, which continues to power war-torn Ukraine, has lost several of its power transmission cables during Russia’s war, and on multiple occasions has had to switch to emergency diesel generators to power its essential cooling systems preventing a meltdown.

The International Atomic Energy Agency’s director-general, Rafael Grossi, plans to visit the Russian-held plant this week. The Vienna-based agency has staff permanently deployed at the plant following Russia’s invasion 13 months ago.

In the meeting, covered exclusively by the Associated Press, Mr. Grossi said the situation at the plant remains tense because of the heavy military presence around it and a blackout that recently struck the facility, something that has occurred repeatedly since Russian forces took it over last year.

Earlier this month, fighting interrupted power supply to the plant for half a day, forcing staff to activate backup generators.

Mr. Grossi expressed alarm at that development. “Each time we are rolling a dice,” he told his agency at the time. “And if we allow this to continue time after time, then one day our luck will run out.”

Messrs. Grossi and Zelensky met at the the city of Zaporizhzhia, which is in Ukrainian-held territory, about 30 miles northeast of the nuclear plant with the same name.

The atomic energy agency announced in January it was placing teams of experts at all four of Ukraine’s nuclear power plants to reduce the risk of accidents.

The agency’s permanent presence at all of Ukraine’s nuclear facilities marked an unprecedented expansion for the agency. That presence includes the now-closed Chernobyl plant whose deadly nuclear accident in 1986 spread fallout over much of Europe.

Mr. Grossi emphasized that his seventh trip to Ukraine underlined his commitment and support for “as long as it takes.”

Also attending the meeting were other agency officials, the head of the Ukrainian presidential office, Andriy Yermak, and the head of nuclear state operator Energoatom, Petro Kotin.

While at Zaporizhzhia, Mr. Zelensky also inspected military positions in the partially-occupied province and awarded soldiers with military honors. He also visited with wounded soldiers at city hospitals as well as an apartment building that Kyiv claims was hit by Russian forces last Wednesday, killing at least one person.

Elsewhere, two people were killed and 29 wounded Monday when Russian forces shelled the Ukrainian city of Sloviansk, in the partially occupied eastern Donetsk region, local officials said.

Video footage of the aftermath showed damaged residential buildings, debris in the streets and vehicles on fire.

Mr. Zelensky described the attack as “terrorism.”

Russia has denied targeting residential areas even though artillery and rocket strikes have hit Ukrainian apartment buildings and civilian infrastructure daily during the war.

The Sloviansk attack followed a typical pattern of long-range shelling adopted by the Kremlin’s forces, especially in recent months as the fighting became deadlocked during the bitterly cold winter months.

In the eastern Donetsk region, some 10 cities and villages were shelled by Russian forces over the previous 24 hours, Ukraine’s presidential office reported Monday.

On Monday morning, Russian missiles hit the city of Avdiivka, damaging residential buildings, a hotel and a courthouse, it said.

Avdiivka’s mayor, Vitali Barabash, said utility companies are being evacuated from the frontline city, as it “resembles more and more a landscape from post-apocalyptic movies.”