Sam’s Club, the US discount warehouse retailer owned by Wal-Mart, has begun restricting purchases of bulk bags of imported rice, amid growing anxieties among small restaurant owners and others over rising global food costs.

Susan Koehler, Sam’s Club’s spokeswoman, said that in most US states customers would be restricted to buying no more than four 20lb (9kg) bags of imported basmati, jasmine and long grain rice.