NEW YORK, USA - US online retail giant Amazon announced a 24 percent increase in quarterly net profit on Thursday and said sales of its electronic book reader, the Kindle, had exceeded expectations.

The Seattle, Washington-based Amazon said net profit rose to 177 million dollars in the first quarter, or 41 cents per share, from 143 million dollars, or 34 cents per share, in the same quarter last year.

Amazon's first quarter results exceeded the expectations of Wall Street analysts, who had been expecting 31 cents per share.

Revenue increased 18 percent to 4.89 billion dollars in the quarter and the company said it expected revenue to grow by between six percent and 17 percent in the current quarter to between 4.3 billion dollars and 4.75 billion dollars.

Amazon released a new version of the Kindle, the Kindle 2, during the first quarter and Jeff Bezos, the founder and chief executive of the company, said Kindle sales had "exceeded our most optimistic expectations."

As previously, Amazon did not provide sales figures for the electronic book readers.

Amazon said North America sales rose 21 percent to 2.58 billion dollars in the quarter while sales from sites in Britain, Germany, Japan, France and China rose 15 percent to 2.31 billion dollars.

By sector, it said media sales, which includes books and other items, grew seven percent to 2.72 billion dollars.

Electronics and other general merchandise sales grew 38 percent to 2.05 billion dollars. Amazon shares lost 4.60 percent to 76.90 dollars in after-hours electronic trading in New York following the release of the results.