The head of the United Nations’ nuclear watchdog is expressing growing anxiety about the safety of the Zaporizhzhia Nuclear Power Plant, after the governor of the Russia-occupied area ordered the evacuation of a town where most plant staff live amid ongoing attacks in the area.

The plant is near the front lines of fighting in the war, and Ukrainian authorities on Sunday said that a 72-year-old woman was killed and three others were wounded when Russian forces fired more than 30 shells at Nikopol, a Ukrainian-held town neighboring the plant.

“The general situation in the area near the Zaporizhzhya Nuclear Power Plant is becoming increasingly unpredictable and potentially dangerous,” International Atomic Energy Agency head Rafael Grossi said in a warning that came Saturday before the latest report of attacks.

“I’m extremely concerned about the very real nuclear safety and security risks facing the plant,” Mr. Grossi added.

Mr. Grossi’s comments were prompted by an announcement Friday by the Russia-installed governor of the partially-occupied Zaporizhzhia province, Yevgeny Balitsky, that he had ordered the evacuation of civilians from 18 settlements in the area, including Enerhodar, which is located next to the power plant, which is Europe’s largest.

The settlements affected are about 30 to 40 miles from the front line of fighting between Ukraine and Russia, and Mr. Balitsky said that Ukraine had intensified attacks on the area in the past several days.

Analysts have for months pointed to the southern Zaporizhzhia region as one of the possible targets of Ukraine’s expected spring counteroffensive, speculating that Kyiv’s forces might try to choke off Russia’s “land corridor” to the Crimean Peninsula and split Russian forces in two by pressing on to the Azov Sea coast.

Some of the fiercest ongoing fighting is in the eastern city of Bakhmut, where Ukrainian forces are still clinging to a position on the western outskirts despite Russia trying to take the city for more than nine months.

Russian Defense Ministry spokesman Igor Konashenkov said Sunday that Moscow’s forces had captured two more districts in the city’s west and northwest, but provided no further details.

Ukraine’s Special Operations Forces on Saturday accused Russia of using phosphorus in the city and on Sunday released a new video showing the telltale white fire from such munitions.

International law prohibits the use of white phosphorus or other incendiary weapons — munitions designed to set fire to objects or cause burn injuries — in areas where there could be concentrations of civilians, though it can also be used for illumination or to create smoke screens.

It wasn’t possible to independently verify where the video was shot or when, but chemical weapons expert Hamish de Bretton-Gordon, a former British army colonel, said it was clearly white phosphorus.

“This is being fired directly at Ukraine positions and this would be a war crime,” he said.

“I expect because the Russians have failed to take Bakmut conventionally, they are now using unconventional tactics to burn the Ukrainian soldiers to death or to get them to flee,” Mr. Bretton-Gordon said.

Russian forces haven’t commented on the claim, but have rejected previous accusations from Ukraine that they had used phosphorus munitions.

In the south, the exiled Ukrainian mayor of the Russia-occupied coastal city of Mariupol, Petro Andryushchenko, said in a Telegram post Sunday that there was evidence that Moscow’s forces had intensified their transfer of tracked vehicles through the city and into the front-line Zaporizhzhia region.

Mr. Andryushchenko claimed that more and more vehicles were being spotted crossing the city “every day.”

He posted a short video showing heavy trucks transporting armored vehicles along an expressway, without specifying where or when it was taken.

In Enerhodar, the town near the nuclear plant, the Ukrainian General Staff said Sunday that the evacuation announced Friday had already begun.

According to an update posted on Facebook, the General Staff said the first residents evacuated were those who took Russian citizenship following the capture of the town by Moscow early in the war.

They were being taken to the Russia-occupied Azov Sea coast, about 120 miles to the southeast.

Mr. Grossi said that operating staff of the nuclear power plant, whose six reactors are currently all in shutdown mode, hadn’t been evacuated as of Saturday but that most live in Enerhodar and the situation has contributed to “increasingly tense, stressful and challenging conditions for personnel and their families.”

He added that IAEA experts at the nuclear site “are continuing to hear shelling on a regular basis.”

“We must act now to prevent the threat of a severe nuclear accident and its associated consequences for the population and the environment,” Mr. Grossi said. “This major nuclear facility must be protected. I will continue to press for a commitment by all sides to achieve this vital objective.”

Elsewhere, Russian shelling on Saturday and overnight killed six civilians and wounded four others in Ukraine’s southern Kherson region, according to a Telegram update published Sunday by the local administration.

Five civilians were wounded in the eastern Donetsk region, the epicenter of the fighting in recent months, a local governor, Pavlo Kyrylenko, reported on Sunday morning.

Meanwhile, Ukrainian forces overnight attacked the largest port in Russia-occupied Crimea with drones, a Kremlin-installed local official said on Telegram early Sunday.

According to the post by the governor of Sevastopol, Mikhail Razvozhayev, 10 Ukrainian drones targeted the city, three of which were shot down by air defense systems. Mr. Razvozhayev said that there had been no damage.

Associated Press