Trees in a vast area -- around one square kilometre at Napitkhali under Chandpai range -- of the world's largest mangrove forest are burning rapidly, posing a threat to natural habitat for many rare species including the famous Royal Bengal Tiger.

Ill-equipped Chandpai range forest guards along with locals have been struggling to douse the fire with water fetched from nearby canals.

Sheikh Mizanur Rahman, conservator of forests, said all 15 wells dug in the area for supply of water during emergency situation were of no use as those were found dry.

Cigarette or oil lamp might have been the source of the fire, said Dhanshagor Station Officer M Golam Mostafa.

Mohammad Mohidullah, divisional forest officer of Sundarban Forest Division (SFD) east wing, said, a number of tube wells are being installed in different parts of the forest to better handle situations like this.

According to eyewitnesses and SFD sources, Tuesday night's fire went out of control as no water was available in the vicinity upto two kilometres.

On March 19, trees and animal habitats of around 250 acres of the forestland were destroyed by another fire.