Wal-Mart Stores Inc on Thursday reported a higher-than-expected 3.1 percent rise in August sales at its U.S. stores open at least a year.

Analysts, on average, were expecting the company's U.S. same-store sales to rise 1.6 percent, according to Reuters Estimates, while Wal-Mart had forecast August sales to rise between 1 percent and 2 percent.

The world's biggest retailer said net sales in the four weeks that ended August 31 rose 9.3 percent to $28.22 billion.