Shares on Wall Street have tumbled, hit by concerns about further inquiries into AOL Time Warner and Citigroup.

The Dow Jones index of leading shares closed 180 points, or 2%, lower at 8,872 points, firmly below the psychologically important 9,000 points level. On Thursday, it closed above 9,000 for the first time in six weeks.

The technology heavy Nasdaq index closed down 42 points at 1380 points.

The decline in share values was largely led by fears that further cases of corporate wrongdoing would emerge.

Market spooked

A report in the Wall Street Journal suggested that New York Attorney General Eliot Spitzer was widening his investigation of Citigroup. The news sent shares in the financial group lower.

Shares in AOL Time Warner also fell, on fears that the media company may have to write down more of its assets. One report suggested that regulators might widen their investigation into the company's finances.

"Raising some governance issues again seems to be the thing that has spooked the market more than anything else," Jeff Kleintop, chief investment adviser at PNC Advisors.

"It's a real slow kind of market, the Dow broke 9,000 so there may be a bit of profit taking," said Robert Basel, a senior trader at Salomon Smith Barney in New York.

Optimism remains

Share movements in Europe and Asia reflected the subdued mood.

The FTSE 100 index of leading UK shares closed 44.9 points lower at 4,389 points, while in Asia, the Nikkei index of leading Japanese shares ended the week up 54 points at 9,867.

But as markets paused for breath after two weeks of rising share prices, some investors predicted returning strength next week, making light of Friday's losses.

"We're seeing a bit of consolidation today, with some profit-taking ahead of the weekend," said one trader.

"But the little summer rally we've seen this week has more momentum."