Ukrainian officials have sought calm after forest fires in the restricted zone around Chernobyl, scene of the world’s worst nuclear accident, led to a rise in radiation levels.

Firefighters said they had managed to put out the smaller of two forest fires that began at the weekend, apparently after someone began a grass fire, and had deployed more than 100 firefighters backed by planes and helicopters to extinguish the remaining blaze.

The fire had caused radiation fears in Kyiv, Ukraine’s capital, which is located about 60 miles south of the Chernobyl exclusion zone. Government specialists on Monday sent to monitor the…