The head of the United Nations nuclear watchdog said on Thursday he worried the world was becoming complacent about the considerable dangers posed by the Russian-controlled Zaporizhzhia atomic plant in Ukraine.

Russian forces captured the plant, Europe's largest, in March and it has repeatedly come under fire in recent months, raising fears of a nuclear disaster. Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), is working to set up a safe zone around the facility.

Grossi, speaking to reporters in the Ukrainian capital Kyiv, said a nuclear accident could happen any day and reiterated the situation at the plant was very precarious.

Zaporizhzhia nuclear plant remains under Moscow control

"I worry that this is becoming routine, that people may believe that nothing has happened so far, so is the director general of the IAEA crying wolf?" he said when addressing reporters during a visit to Ukraine.

"It (an accident) can happen any time and my duty is to do everything I can to prevent that from happening."

The IAEA says it has a permanent presence of up to four experts at Zaporizhzhia. Grossi spoke before traveling to Moscow for talks with Russian officials.