Around 2,500 hectares of forest cover and grassland have been destroyed in the first seven months of this year due to man-made fires.
Fifteen suspects were arrested in July in connection with 150 reported instances of setting fire to forests, said additional conservator general of forests Nishantha Edirisinghe.
He has told BBC Sinhala Service that as much as 2,000 hectares of the ravaged area were grassland.
According to him, many people set fire to forests for fun.
Air Force assistance has to be sought to contain forest fires which has become difficult due to the prevailing dry weather and high winds.