Forest officials said they had found two dead tigers and several deer following the cyclone, the worst to hit Bangladesh since 1991 when a storm killed around 143,000 people.

Officials said better preparedness and an advance warning system had helped save many people this time, but the vast mangrove forest had also largely offset the impact of the cyclone, which triggered a 5-metre water surge from the Bay of Bengal.

According to the forest department's preliminary estimate, the financial loss caused by Sidr to the mangroves would top 10 billion taka (US$145 million), and experts say it might be more.

"Bangladesh is preparing a letter asking emergency funding from the World Heritage Centre for immediate rehabilitation of infrastructure in the Sundarbans," said Shafayat Hossain, a senior official at the Environment and Forest Ministry.

"After final assessment of total damage to the Sundarbans, we will formally seek assistance from the WHC," he said.

Fakhruddin Ahmed, head of Bangladesh's interim government, told donors that Dhaka would need around US$150 million to restore damage to the Sundarbans, the world's largest mangrove area.

"In the backdrop of Sidr, we need to mobilise resources not only for a major forestation programme in the coastal belts, but also to restore the flora and fauna of the Sundarbans," Fakhruddin said.