The Federal Forestry Agency said 3,900 hectares in the fallout zone from the 1986 disaster had been affected by the raging forest fires. The official Interfax newsagency reported that some of the fires in the contaminated areas had ignited as long ago as June. Russian officials had doggedly maintained until Wednesday that fire fighters had combated fires in the fallout zone since temperatures soared in the summer heatwave. But on Wednesday, a forest official said the incidents could not be denied. "There are maps of the (nuclear) contamination, there are maps of the fires," said an official in the affected Bryansk region, which borders Ukraine and Belarus. "Anyone can put the two together. Why deny this information?" Senior officials denied that there was a risk to public health. "There is no reason for panic," said Alexei Bobrinsky, the forestry agency deputy director said. Irina Yegorushkina, of the emergencies ministry, said experts had tested the air after at least six wildfires ignited in Bryansk, but concluded there had been no increase in radiation levels. Large swathes of forest in Bryansk and neighbouring areas were contaminated when the Chernobyl nuclear power plant's Reactor No 4 exploded. The incident happened during a pre-dawn test on April 26, 1986, spewing radioactive clouds over much of the western Soviet Union and northern Europe. The official response to the fires has been subject to unusually strong criticism in the Russian press. Even Vladimir Putin, the prime minister, was condemned for flying in a "water bombing jet" in one of the worst hit regions on Tuesday.