Updated from 4:08 p.m. EDT

U.S. stocks finished a wobbly Thursday with an upward thrust. The day was marked by a flood of corporate earnings statements, evidence of additional turmoil in the financial sector and a fresh serving of economic data.

The Dow Jones Industrial Average, which swung some 815 points during the session, ended the day up 401.35 points, or 4.7%, at 8979.26. The S&P 500 finished up 38.59 points, or 4.3%, at 946.43, and the Nasdaq climbed 89.38 points, or 5.5%, to 1717.71.

Volatility soared during the session, as the CBOE Volatility Index reached 80, a level not seen in its 18 years. After rising 17% to 81 earlier, the index, used as a measure of fear in the market, finished up 3.2% at 71. The Dow swung wildly, down 380 points at its lows and reaching a high with gains of 431 points.

Ahead of Wednesday's trading, Swiss bank UBS ( UBS) received a $5.3 billion cash injection from the Swiss government in exchange for a 9% equity position in the company. UBS and the Swiss National Bank also reached an agreement for UBS to transfer up to $60 billion of currently illiquid securities and other assets from its balance sheet to a separate fund. UBS shares finished up 4% at $17.33.

There was trouble back in the U.S. as well. Bloomberg reported that Citadel Investment Group's largest hedge fund lost as much as 30% this year on bad bets in convertible bonds, stocks and corporate debt. Citadel quickly denied the rumors but said that its performance was hindered by the challenging market.

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