BBC Dhaka Correspondent, Francis Harrison: "The water has been on the ground for more than a month in many areas"

Officials say high tides are affecting rivers in the centre of the country, and flood waters which are already waist-deep in places will continue to rise.

Over 700,000 hectares of farm land have been flooded

Many deaths have been blamed on outbreaks of disease.

The Bangladeshi Foreign Minister, Abdus Samad Azad, has appealed for international aid for millions of people left homeless or destitute.

He said about two-thirds of the country were affected.

Prolonged crisis

Experts at the Flood Forecasting Centre in Bangladesh have said they expect the country to remain inundated until at least mid-September.

People are used to some seasonal flooding, but this year's is longer than usual

They said this year's flood is the longest on record, having lasted more than six weeks already.

United Nations officials believe it is worse than the 1988 flood, which was one of the most devastating this century.

The water has been on the ground for more than a month in many areas. Many people have run out of money to buy food and cannot work because much of the landscape is submerged.

Food shortages

Dhaka Correspondent, Francis Harrison: "People in Bangladesh are already malnourished"

The government has said that more than 700,000 hectares of crop land have been damaged or destroyed. That is expected to result in food shortages a few months from now, which aid workers say could be life threatening for millions of people.

Efforts are now under way to import 1 million tons of food grain, but that will carry an economic price that Bangladesh can not easily afford.

The BBC correspondent in Dhaka, Francis Harrison, says that the country can cope with some seasonal flooding, but the longer the water remains on the ground the more hardship it will cause.

Disease main killer

Disease from lack of sanitation is the main killer

It is the duration of the current flood rather than the depth of the waters - which is not unusually great - that is causing the problems. Lack of sanitation and drinking water mean that disease is the main killer.

Much of Bangladesh is flat delta land easily susceptible to flooding.