Ukraine’s emergency services said a fire covering 20ha was under control, but two other blazes were still raging at the exclusion zone, which was established after the 1986 blast at the plant.

Egor Firsov, who is the head of the state ecological inspection service, said that a Geiger counter used at the site revealed the worrisome data at the disaster area.

“There is bad news — in the centre of the fire, radiation is above normal,” Firsov wrote on Facebook along with a video of a Geiger counter, the New York Post reports.

“As you can see in the video, the readings of the device are 2.3, when the norm is 0.14. But this is only within the area of the fire outbreak.”

But he said the radiation levels in the capital of Kiev, about 100km south of the site, were within the normal range.

The Chernobyl exclusion zone, which remains largely unpopulated, has been mostly overtaken by nature, making it prone to forest fires.

“The problem of setting fires to grass by careless citizens in spring and autumn has long been a very acute problem for us,” Firsov wrote. “Every year we see the same picture — fields, reeds, forests burn in all regions.”