Russia-installed officials in Ukraine’s partly-occupied Zaporizhzhia region said Ukrainian drones on Wednesday attacked Enerhodar, a city serving the Russian-held Zaporizhzhia nuclear power plant.

Russia seized the nuclear plant, Europe’s largest with six reactors, in the early days of the war and each side has since accused the other of staging periodic attacks on the facility.

Russia-installed local officials have reported attacks on Enerhodar, particularly on two electricity substations nearby.

Russian media quoted the city’s authorities as saying at least four drones had attacked Enerhodar.

It said there were no casualties and no details on damage were provided.

“This is a terrorist act,” Russia-installed Acting Mayor Maksim Pukha told Russia’s RIA news agency, saying civil infrastructure and residential areas had been targeted.

“Peaceful residents should in no way be targets of such an attack.”

Each side has accused the other of risking a nuclear catastrophe by attacking the station. Monitors from the U.N.’s nuclear watchdog, the International Atomic Energy Agency, are permanently stationed at the plant.

Russian strike kills 13, injures 113 in Ukraine’s Zaporizhzhia

The governor of the part of Zaporizhzhia region held by Ukraine, Ivan Fedorov, said five drones had attacked the city of Zaporizhzhia, located about 60 km (35 miles) northwest of the plant, across a large reservoir on the Dnipro River.

He posted a picture on Telegram of a large fire he said had been triggered by the attack.

Vladimir Rogov, a senior Russia-appointed official in Zaporizhzhia region, said the attack had disrupted power and water supplies in the city.