A major blaze has broken out in parts of Bangladesh's southwestern Sundarbans, a World Heritage site, ravaging trees in the world's largest mangrove forest, officials said Sunday.

Foresters, nearby villagers and fire-fighters have been trying to douse the flames which engulfed over 20,000 square metres inside the forest at Chandpai Range, 300 km southwest of capital Dhaka, divisional forest officer Mihir Kumar said.

'The foresters reached the scene Saturday afternoon as soon as they confirmed the accident and began their efforts to douse the flames beside Bhola River,' the forest officer told local media.

The efforts to extinguish the blaze were going on Sunday, he added.

The area infested by shrubs and small trees is prone to fire during the winter as it is dry in absence of tidal water at this time, the official said.

The United Nations Educational Scientific and Cultural Organisation announced the forest a World Heritage site in 2007.

The area is also a home to a number of rare species of birds and animals, including the endangered Royal Bengal Tigers.