EU trade commissioner Peter Mandelson has urged countries to maintain rice exports as US retailers start to slap restrictions on the amount of rice customers can buy.

Fears of a global shortage of rice follow reports that leading grain exporters such as India, Egypt, Vietnam and Indonesia had shut off supply in an attempt to curb domestic food inflation.

“If we restrict trade, we're simply going to add food scarcity to the already large problems of food shortages that exist in different countries,” Mandelson told Reuters.

Yesterday, US retail giant Wal-Mart was restricting customers at its cash & carry division Sam's Club from buying no more than four 20 pound bags of rice, while a number of US Costco stores limited customers to buying no more than two bags of rice a day.

“Like our competitors, we're just taking the precautionary step of limiting sales of the very large 20 pound bags of imported jasmine, basmati and long grain white rices, in our case, to four per member,” Sam's Club said in a statement.

“On average, a typical Sam's Club member does not buy more than 80 pounds of rice in one visit. This temporary cap is intended to ensure there is plenty of rice for all our members.”

Last week, the price of rice hit $1,000 a tonne for the first time.