Ukraine yesterday accused Russia of exploiting its position in a nuclear power plant it had seized to target a nearby town in a rocket attack that killed at least 13 people and left many others seriously wounded.

The town Ukraine says Russia targeted - Marhanets - is one that Russia has alleged Ukrainian forces have used in the past to shell Russian forces who are holed up at the Zaporizhzhia nuclear power plant which they took over in March.

Ukraine and Russia have accused each other of imperilling the safety of the vast plant - Europe's largest - by attacking one another in its vicinity.

Rafael Grossi, head of the International Atomic Energy Agency (IAEA), has urged both sides to exercise restraint, warning of the "very real risk of a nuclear disaster."

And foreign ministers from the Group of Seven leading industrialised countries yesterday condemned Russia's occupation of the power plant and called on Moscow to immediately hand back full control of the plant to Ukraine, something Moscow seems unlikely to do.

Moscow says it does not deliberately target civilians in what it calls its "special military operation" in Ukraine aimed at preemptively safeguarding its own security against expansion of the Nato military alliance.

Andriy Yermak, President Volodymyr Zelensky's chief of staff, accused Russia of launching attacks on Ukrainian towns with impunity from the Zaporizhzhia nuclear power plant in the knowledge that it was risky for Ukraine to fight back.

"Eighty reactive rockets fired at residential buildings," Yermak wrote on the Telegram messaging service, referring to the attack on Marhanets.

"The terrorist nation is continuing to fight against civilians. The cowardly Russians can't do anything more so they strike towns ignobly hiding at the Zaporizhzhia atomic power station", he wrote.

Ukraine says around 500 Russian troops with heavy vehicles and weapons are stationed at the plant, where Ukrainian technicians continue to work, reports Reuters.

Russia says its forces are behaving responsibly and doing everything they can to ensure the facility's safety. Moscow has accused Ukrainian forces of shelling the plant, something Kyiv denies.

A senior Ukrainian official suggested a series of explosions at a Russian air base in Crimea on Tuesday could have been the work of partisan saboteurs, as Ukraine denied responsibility for the incident deep in Russian-occupied territory.

Zelensky did not directly mention the blasts in his daily video address but said it was right that people were focusing on Crimea.

"We will never give it up ... the Black Sea region cannot be safe while Crimea is occupied," he said, repeating his government's position that Crimea would have to one day be returned to Ukraine.

Britain, which is helping Ukraine with weapons, intelligence and training, said yesterday that it believed Russia had "almost certainly" established a major new ground force to support its war.

The new force, called the 3rd Army Corps, was based in the city of Mulino, east of Russia's capital, Moscow, the British Defence Ministry said in a daily intelligence bulletin.