Grossi arrived at Europe's biggest nuclear plant to assess potential safety risks after the destruction of the Kakhovka dam, which caused huge floods and exacerbated fears for the facility's safety.

The dam formed a reservoir that provided the cooling water for the plant.

"On the one hand, we can see that the situation is serious, the consequences (of the dam's destruction) are there, and they are real," Grossi, head of the International Atomic Energy Agency, said on a visit to the plant.

"At the same time, there are measures that are being taken to stabilise the situation."

AFP saw Grossi arrive at the plant in a white jeep with the IAEA blue flag attached to it. His car was followed by armoured vehicles.

Grossi's third trip to the plant came as Ukraine pushed ahead with its long-awaited counteroffensive, with fighting intensifying in the Zaporizhzhia region.

His visit was delayed by a day for unexplained reasons.

"Until a few hours ago I was not sure whether I would be able to come here and visit the plant," Grossi said.

He said the trip was "extremely difficult" but also "compact" and "important."

He said he was able to see the plant's cooling pond. "There is sufficient water," Grossi said.

He said he was also able to visit "the thermal plant open switchboard which has been affected by military activity."

Grossi -- who has held talks with both Russian and Ukrainian officials -- had previously proposed measures for the plant's safety but the initiative has so far stalled.

He said he wanted the world to be "aware of the danger" that there could be "a major accident."

"What I expect is the entire international community, the Russian Federation, Ukraine and everybody else supports us, to prevent that from happening."