Bangladesh has banned exports of nearly all the rice it produces to prevent shortages and keep food costs down.

The government said the ban began on Tuesday and will last six months.

Bangladesh is the world's fourth largest rice importer but exports a small amount of aromatic rice, such as Basmati, to other countries.

Rising prices for rice, wheat and other foodstuffs have been hitting poorer people in South Asia badly.

The rises have forced many Bangladeshis to reduce the amount they eat each day. Floods and storms last year compounded global supply problems and pushed prices up.

'Food security'

The Bangladesh government ban follows similar moves in recent weeks by countries such as India, Vietnam and Egypt.

A kilogramme of coarse rice, the staple food of most Bangladeshis, now costs about $0.60 - double what it did a year ago.

The government says it wants to stop exporters exploiting its rice export policy.

"The move will help ensure food security and serve the country's interest," a senior commerce ministry official was quoting as saying by the Daily Star.

Bangladesh produces about 29 million tonnes of coarse rice annually for its 140 million people and imports some three million tonnes.

Rice exports were worth about $5.4m in the first eight months of the fiscal year (July-June), officials say. Imports cost about $600m - 10 times higher than for the same period the year before.

Officials have said they fear social unrest unless they act over food, and many people have been queuing to buy government-subsidised rice.

Bangladesh's most important rice harvest, called Boro, has now begun and the government expects a bumper crop this year.

Correspondents say this should ease problems, at least in the short term.