U.S. stocks extended losses on Friday after steep sell-off in the previous session as concerns over European debt problems and U.S. economic strength still weighed on the market.

Investors were depressed after the Dow Jones industrial average plunged more than 400 points in a single day, a reminder of the big turmoil in the market last week.

Concerns over the debt situation in Europe still lingered in the market. Major banks were under heavy selling pressure as they were more exposed to European debt.

Technology sector was also hit hard, dragged by Hewlett-Packard, whose shares plunged more than 20 percent after several Wall Street analysts downgraded its stock. The tech-heavy Nasdaq suffered its first four-day losing streak since June.

Worries about an economic downturn in the United States also haunted equities. After Morgan Stanley and Goldman Sachs slashed their forecasts for global economic growth on Thursday, Citigroup and JPMorgan Chase cut their U.S. growth forecasts as the global economy slows and officials struggle to stem Europe's sovereign- debt crisis.

As of Friday's close, the Dow Jones industrial average lost 172. 93 points, or 1.57 percent, to 10,817.65. The Standard & Poor' s 500 dropped 17.12 points, or 1.50 percent, to 1,123.53. The Nasdaq Composite Index declined 38.59 points, or 1.62 percent, to 2,341. 84.