Relief workers in Bangladesh say they have reached the last remaining pockets of the country devastated by last week's cyclone that killed some 3,500 people and displaced millions others.

The military is flying helicopters and cargo planes to deliver badly needed food, medicine, tents and clean water.

Relief officials say many victims have lost everything and will need months to recover. They also warned the death toll could climb significantly after all the victims in isolated areas are accounted for.

The World Bank offered up to $250 million to help the nation recover from the deadly storm, while the United Nations said it had authorized almost $9 million in aid.

The director of U.S. Foreign Assistance, Henrietta Fore is in Dhaka to offer more than $2 million in aid.

Two U.S. naval ships, U.S.S. Essex and The Kearsarge carrying some 30 helicopters are scheduled to arrive in the Bay of Bengal by the end of the week to help distribute 35 tons of emergency aid.

The Australian government pledged $3 million toward emergency relief, while the European Union more than $9.5 million.

Cyclone Sidr is the worst natural disaster in Bangladesh since 1991, when a cyclone and storm surge killed around 143,000 people.

The head of Bangladesh's emergency government, Fakhruddin Ahmed, said the country was facing a national crisis and called on Bangladeshi citizens to help those in need.

Some information for this report was provided by AFP and AP.