Stocks surged Thursday, rebounding from Wednesday's steep losses, as a regional Federal Reserve survey eased concerns about slowing economic growth and strong earnings from companies such as Motorola and Altria buoyed investor confidence.

The Dow Jones industrial average (search) was up 206.24 points, or 2.06 percent, to close at 10,218.60. The Standard & Poor's 500 Index (search) was up 22.45 points, or 1.97 percent, to finish at 1,159.95. The Nasdaq Composite Index (search) was up 48.65 points, or 2.54 percent, to close at 1,962.41.

The Dow posted its biggest point rise in a day since April 2, 2003, when the average rose 215.2 points. The Dow and the S&P 500 had their biggest one-day percentage gains since October 2003.

The market rally came a day after The New York Stock Exchange (search), the world's biggest stock exchange, struck a deal that will merge the Big Board with electronic market Archipelago Holdings Inc. (AX). Archipelago, which trades on the Pacific Stock Exchange, soared 66 percent, or $11.87 to $29.87.

Bargain-minded buyers jumped back into the market a day after concerns about rising inflation eclipsed strong earnings, sending stocks sharply lower and pushing the Dow to a whisker away from ducking under the 10,000 mark.

"Solid earnings, the absence of any inflationary readings and the midday trigger of a stronger-than-expected Philly Fed opened the dam," said John Caldwell, chief investment strategist at McDonald Financial Group, part of KeyCorp.

But some investors were skeptical about the strength of the rally following a number of days of sharp swings.

"It's a snap-back rally -- I still think the path of least resistance is down and that you probably ought to be selling into this rally," said Tim Heekin, director of trading at San Francisco investment bank Thomas Weisel Partners.

The market extended its gains in early afternoon, after the Federal Reserve Bank of Philadelphia, or Philly Fed, said its business activity index rose to 25.3 from 11.4 in March -- more than double the amount economists had forecast. The news eased investors' concerns about slowing economic growth.

"The earnings news has been by and large pretty good," McDonald Financial's Caldwell said. "Motorola and Nokia were good and helped tech, Nucor is helping the steel (sector) and UPS is driving the transports."

But Caldwell cautioned that investors were "grasping at anything to justify moves in the market.

"The bottom line is you're talking about a period of slowing economic growth, slowing earnings growth and rising inflation -- that's what people are worried about," Caldwell continued. "But it's also the consensus forecast for this year, so why the big surprise?

"People are getting caught up in the moment and losing sight of the forest through the trees."

Another positive for stocks was Fed Chairman Alan Greenspan saying Thursday that the United States does not seem to be heading towards stagflation, the 1970s-style combination of high inflation and lackluster economic growth.

After the closing bell, Web search leader Google Inc. (GOOG) posted a quarterly profit that blew past year-earlier results. Its shares leaped $10 to $214.22 from its Nasdaq close at $204.22.

"Outstanding is the only way to describe the results," said Robert Lutts, chief investment officer at Cabot Money Management Inc., which owns some shares of Google. "They have people all over the world clicking and paying."

Nokia (NOK) gained 6.6 percent, or $1.01, to $16.35, after reporting double-digit growth in the first quarter and raising its earlier estimate of the global mobile handset market in 2005, surprising analysts. Its rival, Motorola (MOT), also had better-than-expected earnings on a solid rise in sales; Motorola was up 6.7 percent, or $1.00, at $15.93.

On the Dow, the best-performing components included Altria Group Inc. (MO), which rose 4.1 percent, or $2.56, to $65.31; Walt Disney Co. (DIS), up 3.9 percent, or $1.05, at $27.67; and Microsoft Corp. (MSFT), up 4 percent, or 96 cents, at $25.28.

EBay Inc. (EBAY) shed 3 cents to $33.08, despite announcing better-than-expected results after the bell Wednesday, thanks to a surge in new customers and strong growth overseas. Optimistic executives also brightened their outlook for the rest of year, but worries about increased competition dogged the stock.

Trading was heavy, with 1.84 billion shares changing hands on the New York Stock Exchange, above the 1.46 billion daily average for last year. About 2 billion shares were traded on Nasdaq, above the 1.81 billion daily average last year.

Advancers outnumbered decliners by about 3 to 1 on both the New York Stock Exchange and the Nasdaq.

The Russell 2000 index, which tracks smaller company stocks, was up 12.88, or 2.20 percent, at 597.84.

Overseas, Japan's Nikkei stock average slid 0.94 percent. In Europe, France's CAC-40 rose 0.03 percent, Britain's FTSE 100 fell 0.05 percent and Germany's DAX index was up 0.36 percent.

Reuters and the Associated Press contributed to this report.