Bangladesh has asked foreign donors and development partners for hundreds of millions of dollars to help its economy after floods destroyed crops and left millions homeless, a government official has said.

Bangladesh's economic growth might slow to 6.8 percent from a target of 7 percent and the budget deficit would widen due to an increase in unforeseen expenditure caused by the floods, officials said.

"The government has formally asked them to provide an additional budgetary support and food aid to tackle the post flood situation," Mohammad Aminul Islam Bhuiyan, secretary of the Economic Relations Division, told Reuters.

"So to tackle the budget deficit we requested the development partners to provide initially $150 million, but after the final assessment we will require more assistance from them."

An official who attended a meeting with the World Bank and the Asian Development Bank on Sunday said the two organisations might provide $300 million and $150 million respectively as budgetary support over the next four months.

Officials said that initial assessments showed the worst affected sectors are agriculture, communications, education and health. The floods affected nearly 700,000 ha (1.73 million acres) of farmland, washing away mainly rice crops.

The U.N.'s World Food Programme (WFP) said in a statement on Monday it would distribute rice to more than 800,000 people in 10 badly affected districts by the end of August. It said it had already distributed rice to 335,000 people at the start of the month.

The floods that began around the middle of July have killed nearly 600 people, the health ministry said.