The head of the UN atomic agency on Tuesday said Europe's largest nuclear plant was free from danger, a day after Russia expelled the power station's director.

Russian forces had detained Ihor Murashov, the chief of the Zaporizhzhia nuclear plant in southern Ukraine, for two days before releasing him on Monday.

Moscow and Kyiv have traded blame for months for shelling near the Russian-held facility that sparked fears of a nuclear disaster.

Asked about any security risk to the plant during a trip to the Armenian capital Yerevan, International Atomic Energy Agency (IAEA) chief Rafael Grossi said there was "no risk at all".

"The most important thing concerning Murashov is that he has been freed... and is once again with his family," he added.

Ukraine's nuclear agency on Saturday said Murashov was detained by a Russian patrol as he was travelling from the plant to the Russian-controlled city of Energodar.

He was freed in Ukrainian-held territory on Monday.

The plant, located in the Zaporizhzhia region that was annexed by Russia last week, has been occupied by Moscow's forces since March and is close to the front line.

Grossi is due to travel to Moscow and Kyiv this week to discuss setting up a nuclear safety and protection zone around the Zaporizhzhia site, the IAEA announced in a statement on Tuesday.