Russian forces have begun an assault on two key cities in the eastern Donetsk region and kept up rocket and shelling attacks on other Ukrainian cities, including one close to Europe’s largest nuclear power plant, Ukrainian officials said.

Both cities of Bakhmut and Avdiivka had been considered key targets of Russia’s ongoing offensive across Ukraine’s east, with analysts saying Moscow needs to take Bakhmut if it is to advance on the regional hubs of Sloviansk and Kramatorsk.

“In the Donetsk direction, the enemy is conducting an offensive operation, concentrating its main efforts on the Bakhmut and Avdiivka directions. It uses ground attack and army aviation,” the Ukrainian General Staff said on Facebook.

Russian shelling killed five civilians and injured 14 others in the Donetsk region in the last day, Donetsk governor Pavlo Kyrylenko wrote on Telegram on Saturday, saying two died in Poprosny, and one each in Avdiivka, Soledar and Pervomaiskiy.

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Ukrainian President Volodymyr Zelensky as he visits the Kharkiv region (Ukrainian Presidential Press Office via AP)

The governor of the eastern Dnipropetrovsk region said three civilians were injured after Russian rockets fell on a residential neighbourhood in Nikopol, a city across the Dnieper River from the Zaporizhzhia nuclear power station. The nuclear plant has been under Russian control since Moscow’s troops seized it early in the war.

“After midnight, the Russian army struck the Nikopol area with (Soviet-era) Grad rockets, and the Kryvyi Rih area from barrel artillery,” Valentyn Reznichenko wrote on Telegram.

Ukrainian authorities also said a Russian missile attack overnight damaged unspecified infrastructure in the regional capital of Zaporizhzhia. On Thursday, Russia fired 60 rockets at Nikopol, damaging 50 residential buildings in the city of 107,000 and leaving residents without electricity.

Rafael Grossi, head of the International Atomic Energy Agency, warned this week that the situation was becoming more perilous day by day at the Zaporizhzhia plant.

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Debris hangs from a residential building heavily damaged in a Russian bombing in Bakhmut, eastern Ukraine (Francisco Seco/AP)

“Every principle of nuclear safety has been violated” at the plant, he said. “What is at stake is extremely serious and extremely grave and dangerous.”

He expressed concern about the way the plant is being operated and the danger posed by the fighting going on around it. Experts at the US-based Institute for the Study of War said they believe Russia is shelling the area intentionally, “putting Ukraine in a difficult position”.

The Ukrainian company operating the nuclear power station said on Saturday that Russian troops are using the plant’s basement to hide from Ukrainian shelling and have barred its Ukrainian staff from going there.

“Ukrainian personnel do not yet have access to these premises, so in the event of new shelling, people have no shelter and are in danger,” Enerhoatom, a Ukrainian state enterprise, said on its Telegram channel.

Enerhoatom said on Friday that Russian rockets had damaged the plant’s facilities, including a nitrogen-oxygen unit and a high-voltage power line. Local Russian-appointed officials acknowledged the damage, but blamed it on alleged Ukrainian shelling.

In Ukraine’s south, two civilians were seriously injured on Saturday after Russian forces fired rockets on the Black Sea port of Mykolayiv before dawn, according to regional authorities. That followed a Friday afternoon attack on Mykolayiv that killed one person and wounded 21 others.

In the north, Ukraine’s second-largest city of Kharkiv and its surrounding area also came under Russian rocket fire again overnight, according to regional governor Oleh Syniehubov. A 18-year-old in Chuhuiv, a town near Kharkiv, had to be taken to hospital on Saturday after he picked up an unexploded shell.

Both Chuhuiv and Kharkiv have endured sustained Russian shelling in recent weeks, due to their proximity to the Russian border.

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Volodymyr Zelensky described the situation in the east as ‘indescribably difficult’ (Ukrainian Presidential Press Office via AP)

The neighbouring Sumy region, which also borders Russia, has also seen near-constant shelling and missile strikes. Its regional governor said on Saturday the province was hit more than 60 times from Russian territory over the previous day, and one wounded civilian had to be admitted to hospital.

On the ammunition front, Russia has begun using Iranian combat drones in the war, Ukrainian presidential adviser Oleksiy Arestovych said in a YouTube address, adding that Tehran had transferred 46 drones to the Russian army.