US shares drop as market opens

US stocks tumbled on the market opening today amid a rout in global trading after the US credit rating was downgraded for the first time.

At the opening, the Dow Jones industrial average was down 192, or 1.7%, to 11,252. The S&P 500 was down 23, or 2% to 1,176 and the Nasdaq down 64, or 2.5%, to 2,468.