A view shows a sign reading NPP (nuclear power plant) near the Zaporizhzhia Nuclear Power Plant. Reuters
Shells hit a high-voltage power line at the Zaporizhzhia plant, prompting operators to disconnect a reactor despite no radioactive leak being detected. The plant was captured by Russian forces in early March in the opening stage of the war but it is still run by its Ukrainian technicians.
Earlier this week, the United Nations nuclear watchdog appealed for access to the plant, which Washington says Russia is using as a battlefield shield.
Ukraine's state nuclear power company Energoatom blamed Russia for the damage at the power station.
A serviceman with a Russian flag on his uniform stands guard near the Zaporizhzhia Nuclear Power Plant. Reuters
Ukrainian President Volodymyr Zelensky said Moscow was responsible and accused it of committing "an open, brazen crime, an act of terror", calling for sanctions on the entire Russian nuclear industry.
Russia's defence ministry accused Ukrainian forces of shelling the plant, saying a leak of radiation had been avoided only by luck.
It said that as a result, the generating capacity of one unit had been reduced and power supply to another had been cut. In addition, the nearby city of Enerhodar had power and water supplies problems, a ministry statement said.
Energoatom said the plant, about 200 km (160 miles) northwest of the Russian-held port of Mariupol in southeast Ukraine, was still operational and no radioactive discharges had been detected.
The United Nations nuclear watchdog appealed for access to the plant.
Further east, both sides claimed small advances while Russian artillery bombarded towns and villages across a wide area in a now-familiar tactic.
Kharkiv, Ukraine's second city, was subjected to renewed shelling early on Friday, the mayor said. "All of Kharkiv heard the sounds," Kharkiv Mayor Ihor Terehov said on Telegram. "The rescue teams are on site."
Details of any casualties or damage were not immediately available.
The southern city of Mykolaiv was shelled on Friday night and one person was killed, Mayor Oleksandr Senkevych said on Telegram. Twenty-two people were injured. Twenty-one private homes and five residential apartment buildings suffered damage, the mayor said.