NEW YORK - Amazon.com Inc. said Thursday that its fourth-quarter profit rose 9 percent and easily surpassed analysts' forecasts. That result, plus an optimistic forecast, sent Amazon shares soaring 13 percent in extended trading.

In December, Amazon called the holiday season its "best ever," and the earnings report backed up the idea that the online retailer is not being seriously hurt by reductions in consumer spending. Amazon said its revenue in the current quarter should be $4.53 billion to $4.93 billion. Analysts are expecting $4.57 billion.

Shares of the Seattle-based company shot up $6.60, or 13.2 percent, to $56.60 in after-hours trading following the release of the earnings report. The stock had fallen 36 cents to finish regular trading at $50.

Amazon said its fourth-quarter profit was $225 million, or 52 cents per share, compared with $207 million, or 48 cents per share, in the same quarter a year earlier. Analysts, on average, had been expecting 39 cents per share, according to Thomson First Call.

Revenue rose 18 percent to $6.7 billion, exceeding analyst estimates of $6.4 billion. If not for the strengthening dollar, which diminishes the value of sales in other currencies, Amazon said its revenue would have risen 24 percent.

Sales of items such as books, CDs and DVDs climbed 9 percent to $3.64 billion, and sales of electronics and other merchandise rose 31 percent to $2.89 billion.

The recession's effects may have shown up in one key figure -- Amazon's gross profit margin. It declined to 20.1 percent, from 20.6 percent in the fourth quarter of 2007.

In a conference call with reporters, Chief Financial Officer Tom Szkutak said the fall could be attributed in part to price cuts.

Amazon's net shipping cost rose, up 32 percent year over year to $242 million.

ASSOCIATED PRESS