The head of the International Atomic Energy Agency decried as “very dangerous” Russia’s temporary occupation of the Chornobyl nuclear power station and offered to help Ukraine repair damage caused to the stricken plant.

Rafael Grossi, the IAEA’s director general, was speaking on the 36th anniversary of the world’s worst civil nuclear power disaster at the plant when its fourth reactor caught fire and exploded on April 26, 1986.

Ukrainian President denounced Russian behaviour at the site and said Moscow had shown total disregard for nuclear safety on the anniversary by sending rockets over Chornobyl and two other functioning nuclear power stations.

Russian troops moved into the highly contaminated “exclusion zone” surrounding the Chornobyl plant days after the beginning of war. They withdrew late last month.

“The situation was absolutely abnormal and very, very dangerous”, - Grossi said.