Dow jumps 400 as government pledges bank aid

Major stock indexes surged more than 4 percent, including the Dow Jones industrials, which at times jumped more than 400 points. A rebound had been expected at some point after the Dow lost nearly 2,400 points over eight sessions. But the gains don't necessarily signal that the market is now finished with the intense volatility of recent weeks.

Dave Rovelli, managing director of U.S. equity trading at Canaccord Adams in New York, said that while the market had been expecting a snapback rally after steep declines logged since last month, sustainable gains could prove more elusive.

"Everybody knew that we were going to have an up day eventually," he said. "When everybody expects something it never really comes true."

He said that while he expects a rally Monday, it doesn't necessarily signal an end of the market's troubles.

In the first half-hour of trading, the Dow Jones industrial average rose 358.10, or 4.24 percent, to 8,809.29 after rising 440 points in the early going.

Broader stock indicators also jumped. The Standard & Poor's 500 index advanced 41.81, or 4.65 percent, to 941.03, and the Nasdaq composite index rose 75.52, or 4.58 percent, to 1,725.03.