Firefighters have been battling a blaze that broke out at the weekend in the wooded zone around the ruined Chernobyl reactor that exploded in 1986 in the world's worst nuclear accident.

On Tuesday, the fire covered some 35 hectacres (87 acres), having tripled in size due to strong winds, the emergencies service said in a statement, adding that background radiation levels remained "within normal limits".

Kiev has mobilised helicopters and around 100 firefighters, with firefighting planes dropping tons of water on the fire.

Police said the blaze broke out after a man set fire to dry grass near the exclusion zone.

The man was detained by police.

On Sunday, Yegor Firsov, acting head of Ukraine's state ecological inspection service, said in a Facebook post that radiation levels at the centre of the fire were higher than normal.

But government agencies rejected that finding and Firsov himself later withdrew his remarks.

The Chernobyl power station contaminated a large swathe of Europe when its fourth reactor exploded in April 1986, with the area immediately around the plant the worst affected.

People are not allowed to live within 30 kilometres (18 miles) of the power station, which is some 100 kilometres (62 miles) north of Ukraine's capital Kiev.

The three other reactors at Chernobyl continued to generate electricity until the power station finally closed in 2000.

A giant protective dome was put in place over the fourth reactor in 2016.

Fires occur regularly in the forests near the Chernobyl power plant.