Capacity was reduced at one unit of the South Ukraine nuclear power plant after Russian attacks damaged the country's electricity transmission system, nuclear firm Energoatom said on Wednesday.

"No accidents occurred at the South Ukraine nuclear power plant," Energoatom said on Telegram messenger.

Instead, it said output was reduced after "hostile shelling of Ukrenergo's infrastructure" and "significant fluctuations in the parameters of the grid".

Energoatom said electricity generation at the unit was reduced by 33% but did not specify when this occurred.

Ukraine's energy infrastructure has been subjected to increased Russian missile and drone attacks in recent months.

Officials have said the country has lost about half of its generating capacity and now relies mainly on energy generated by three nuclear power plants.

A fourth, the Europe's biggest, Zaporizhzhia NPP, was occupied by Russia at the beginning of the war and is currently not in operation.