More than 300 firefighters aided by several firefighting aircraft were working to contain the blazes, which in recent days have been exacerbated by high winds.

Authorities have more than doubled the number of firefighters in the area since Monday. The extent of the blazes has not been disclosed for the past two days.

Authorities have attributed blazes in the Chernobyl zone and elsewhere in Ukraine in recent weeks to relatively dry conditions after a winter that lacked sufficient precipitation and snow cover.

Environmental experts fear the fires could stir up radioactive ash in the ground. Ukraine's State Emergency Service has said the radiation levels have appeared to be within the acceptable norm.

A senior environmental official, Egor Firsov, said at the weekend that radiation in the area was detected at 16 times higher than normal background levels.

A 27-year-old resident of a settlement near the exclusion zone is under investigation on suspicion of having started at least one of the local fires.

The man, who could face up to five years in prison, is believed to have been burning grass and rubbish, and was unable to contain the fire because of windy weather, according to a police statement.

The 1986 reactor meltdown and explosion at the Chernobyl nuclear power plant, about 100km north of Kiev, is considered the worst nuclear disaster in history.

Australian Associated Press