ENERGODAR, June 15 (AFP) - UN nuclear chief Rafael Grossi on Thursday (Jun 15) said the situation at the Moscow-occupied Zaporizhzhia atomic power plant in Ukraine was "serious" but being stabilised as Kyiv reported progress in its counteroffensive.

Fears for Europe's biggest nuclear plant, which have persisted throughout Moscow's Ukraine offensive, have been exacerbated by the destruction of a dam that provided the cooling water for the plant.

Grossi, whose trip was delayed by a day as fighting intensified in the southeastern region of Zaporizhzhia, arrived to assess potential risks.

"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," said Grossi, head of the International Atomic Energy Agency.

"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.

He described the trip as "extremely difficult" but "important".

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

"Of course, this is a result of increased tension in the area."

He said he was able to see the plant's cooling pond and "there was sufficient water".

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

Grossi's third trip to the plant, which fell to Moscow's forces early in their offensive, came as Ukraine, bolstered with Western weapons and training, pushed its long-awaited effort to force Russian troops off its territory.