Hundreds of firefighters on Monday battled a forest blaze in Ukraine's Chernobyl exclusion zone while officials insisted there was no risk to the ruined reactor and nearby storage facilities for nuclear waste.

"There is no threat to the Chernobyl nuclear power plant and the storage facilities," Volodymyr Demchuk, a senior official from Ukraine's emergency service, said in a video statement late Monday.

The fire broke out 10 days ago at the scene of the world's worst nuclear accident in 1986.

Kiev has mobilized helicopters and more than 400 firefighters, with planes dropping tons of water on the fire. Ukraine's Emergency Situations Service said it was still fighting the fires, but that the situation was under control.

However, videos on Sunday showed plumes of black smoke billowing into the sky and trees still ablaze, with firefighters in helicopters trying to put out the fires. Aerial images of the 30 kilometer exclusion zone around the plant, site of the world's worst nuclear accident in 1986, showed scorched, blackened earth and the charred stumps of still smouldering trees.