Kyiv, Jul 19 (IANS): Russian soldiers have been killed and injured in a mysterious "unexplained incident" at the occupied Zaporizhzhia nuclear power plant in Ukraine, it has been claimed, media reports said.

Dmytro Orlov, the mayor of Enerhodar where the station is based, said the troops were "so scared that they ran around in a panic", with some now in intensive care in hospital, Daily Mail reported.

The cause of the sudden hysteria is not known, although Russian President Vladimir Putin's men had been using the power plant to store many of their weapons, including missile systems.

The President of Ukrainian nuclear agency Energoatom had warned on Friday that the situation was "extremely tense", with up to 500 Russian soldiers controlling the site, Daily Mail reported.

"The occupiers bring their machinery there, including missile systems, from which they already shell the other side of the river Dnipro and the territory of Nikopol," Petro Kotin said, referring to the city across the water.

"They physically control the perimeter. The occupiers' heavy machinery and trucks with weapons and explosives remain on the territory of the Zaporizhzhia nuclear power plant," he said.

According to Mayor Orlov, nine soldiers were taken to the local hospital with varying degrees of severity.

He said: "One of them was brought in in a serious condition and has been put in intensive care. 'Some have died but we cannot name their exact number at the moment."

"They were so frightened that they ran around the territory of the station in a panic, and blocked two shifts of operational personnel at the plant for a very long time instead of changing shifts as they were supposed to," he said, Daily Mail reported.

The Zaporizhzhia plant, which creates around 20 per cent of Ukraine's electricity, was seized by Russian forces on March 4 and they now control the administrative buildings and the station.