Western countries have called for Moscow to withdraw its troops from the Zaporizhzhia plant, but there has been no sign so far of Russia agreeing to do that. The plant was captured by Russian forces in early March but is still run by Ukrainian technicians.

The plant dominates the south bank of a vast reservoir on the Dnipro river that cuts across southern Ukraine.

Ukrainian forces controlling the towns and cities on the opposite bank have come under intense bombardment from the Russian-held side.

Three civilians, including a boy, were wounded in overnight shelling of one of those towns, Marhanets, the governor of the Dnipropetrovsk region Valentyn Reznichenko said.

Kyiv has said for weeks it is planning a counter-offensive to recapture Zaporizhzhia and neighbouring Kherson provinces, the largest part of the territory Russia seized after its February 24 invasion and still in Russian hands.

Donetsk regional governor Pavlo Kyrylenko said there was more shelling of the eastern town of Kramatorsk on Friday. Video posted on his Telegram channel showed major damage to private homes.

Three people were killed, the town's mayor said in a Facebook post.

Ukraine's military said its artillery destroyed a Russian ammunition depot near a bridge about 130km down the Dnipro river from the nuclear plant and said it could now strike nearly all Moscow's supply lines in the occupied south.

"Today the Ukrainian armed forces struck the last, the fourth, bridge linking the left and right banks," Serhiy Khlan, an official in the mostly Russian occupied Kherson region, wrote on Facebook on Friday.

"This means the Russians no longer have any possibility of bringing in new equipment."

There was no comment from Russian authorities on the reports, and Reuters could not confirm them independently.

The United States is supplying Ukraine with weapons to defend itself and Russia has accused Washington of being directly involved in the war.

On Friday, a senior Moscow official said if the US Senate succeeded in passing a law to single out Russia as a "state sponsor of terrorism", diplomatic ties would be badly damaged and could even be broken off.

Ukrainian President Volodymyr Zelenskiy has urged the United States and other countries to give Russia that designation, accusing its forces of targeting civilians, which Moscow denies.

"After everything that the occupiers have done in Ukraine, there can be only one approach to Russia - as a terrorist state," Zelenskiy said in his nightly address on Friday.

Ukraine's Energoatom agency, whose workers still operate the Zaporizhzhia plant under Russian occupation, said the power station was struck five times on Thursday, including near where radioactive materials are stored.

Russia says Ukraine is recklessly firing at the plant. Kyiv says Russian troops struck it themselves, and are also using the plant as a shield to provide cover while they bombard nearby Ukrainian-held towns and cities.

"We understand that the invaders are hiding behind such a shield because it is not possible to strike there," Natalia Humeniuk, an official with Ukraine's southern military command, told Ukrainian national television.

Russia's former president Dmitry Medvedev dismissed such accusations as "100 per cent nonsense".

Nuclear experts fear fighting might damage the plant's spent fuel pools or the reactors.

"There is no nuclear power plant in the world that was designed to operate in a war situation," Mycle Schneider, co-ordinator of the World Nuclear Industry Status Report, said.

Ukraine's General Staff on Friday reported widespread shelling and air attacks by Russian forces on scores of towns and military bases, especially in the east where Russia is trying to expand territory held on behalf of separatist proxies.

Australian Associated Press