US shoppers maintained their focus on keeping costs down as they embarked on the "back-to-school" shopping season, favouring Wal-Mart and other low-cost retailers over department and fashion stores, according to August sales figures.

Wal-Mart saw sales at its supercentre and discount stores open at least a year rise 2.8 per cent, led by its grocery and health sales, which includes pharmacy. Together with its Sam's Club warehouse stores, sales rose 3 per cent, ahead of its forecast of between 1 and 2 per cent growth.