KYIV - Forest fires, which broke out around the Chernobyl nuclear power plant due to hostilities, cover more than 10,000 hectares, Ukrainian Ombudswoman Lyudmyla Denisova said Sunday.

"We have recorded 31 fires, which caused an increased level of radioactive contamination in the air," Denisova wrote on Facebook.

Ukrainian firefighters are unable to reach the area, which is controlled by Russian forces, Denisova added.

The Chernobyl nuclear plant, some 110 km north of Kiev, suffered one of the worst nuclear accidents in human history on April 26, 1986.

On Feb 24, Mykhailo Podoliak, advisor to the head of the President's Office of Ukraine, said Russian forces had seized the Chernobyl nuclear power plant.