At least 2,000 people are now reported dead after a powerful cyclone ripped through southern and central Bangladesh, officials say.
The government expects the figure to rise further, as parts of the affected area are still inaccessible.
Rescuers are trying to reach hundreds of thousands of survivors but debris and floods are hampering their efforts.
Cyclone Sidr destroyed or damaged tens of thousands of homes, brought down power lines and wiped out vital crops.
A huge relief operation is under way but the true extent of the destruction is only now emerging, the BBC's Mark Dummett in Dhaka reports.
Military helicopters and ships joined the rescue efforts on Saturday, helping deliver supplies and medical assistance to some of the most remote areas.
Bangladesh's director general of disaster management, Masood Siddiqui, told the BBC that the death toll had reached 2,000 people.
"We are expecting that thousands of dead bodies may be found within a few days," Shekhar Chandra Das, deputy head of the government's disaster management office, told AFP.
"We have not been able to collect information about casualties in many remote and impassable places due to the disruption to communications," he said.
The severity of the storm not only smashed homes, but destroyed vital food sources too. Officials say that in many areas 95% of rice which was awaiting harvest has been destroyed, and shrimp farms and other crops simply washed away.
Elephants are being used to help clear roads
"Many people are homeless, crops and livelihoods have been destroyed and this is going to put great pressure on the government, the economy, and the people themselves, particularly as this comes only a few months after floods devastated the northern part of the country," Suman SMA Islam, humanitarian assistance co-ordinator for the aid agency Care, told Reuters.
As well as helicopters being used to ferry supplies to hard hit areas, ships are also at work clearing channels blocked with sunken vessels.
On land, elephants are being employed to clear some of the heavier debris from roads.
The storm hit Bangladesh late on Thursday, with winds rising to 240km/h (150mph).
It passed through the capital Dhaka hours later, before dying down in the north-east of the country.
The biggest challenge for southern Bangladesh will now be reconstruction, the BBC's Mark Dummett says.
Trail of destruction
One witness in the south-western Bagerhat district told the news agency AFP that the storm had destroyed 80% of the homes in his village.
"I cannot describe how devastating it was. It was like doomsday, the most frightening five hours of my life. I thought I would never see my family again," said local businessman Mollik Tariqur Rahman.
"There is a trail of destruction everywhere. We can't even detect exactly where our houses were built - only a few are left and they do not have roofs," he said.
Many people are thought to have been killed as falling trees levelled fragile houses made of thatch, wood and tin.
The storm triggered 5m (16ft) tidal surges in many of the affected districts. Rivers flowing into the Bay of Bengal were said to be swollen and rising.
At least 150 fishing boats in the Bay of Bengal have failed to return to shore.
Hundreds of fishermen are feared missing.
Amid a virtual national blackout, the authorities have been struggling to get food, medicine, tents and blankets to the affected areas.
An official from the UN World Food Programme said the most urgent needs were food, water purification tablets, and medicines.
The WFP is sending energy biscuits for 400,000 people. The government, the Red Crescent and other NGOs are also sending teams.
Bangladesh developed a network of cyclone shelters and a storm early-warning system, after a cyclone killed more than 500,000 people in 1970.
Casualties from cyclones have been significantly reduced as a result, officials say.
Southern Bangladesh is hit every year by cyclones and floods, but Cyclone Sidr is the most destructive storm to hit the country in more than a decade.
Another storm in 1991 left some 143,000 dead.