The Seattle-based company's admission followed reports that books with gay or lesbian themes had been pulled from the rankings, a move which could hurt their sales.

Amazon, in a statement distributed late Monday to several technology blogs, denied that books with homosexual themes were targeted and said that numerous categories of books had been affected.

"This is an embarrassing and ham-fisted cataloging error for a company that prides itself on offering complete selection," Amazon said.

"It has been misreported that the issue was limited to gay and lesbian themed titles -- in fact, it impacted 57,310 books in a number of broad categories such as health; mind and body; reproductive and sexual medicine; and erotica.

"This problem impacted books not just in the United States but globally," Amazon said. "It affected not just sales rank but also had the effect of removing the books from Amazon's main product search.

"Many books have now been fixed and we're in the process of fixing the remainder as quickly as possible, and we intend to implement new measures to make this kind of accident less likely to occur in the future," it said.

Among the books which lost their rankings were James Baldwin's "Giovanni's Room" and Annie Proulx's "Brokeback Mountain," according to Publishers Weekly.

The disappearance of particular books from the Amazon sales charts was first noticed by Mark Probst, the author of a gay romance, who wrote about it on his personal blog.

Probst queried Amazon about it and was told that the company was excluding "adult" material from searches and bestseller lists "in consideration of our entire customer base."

Several petitions condemning Amazon began circulating online following the reports that certain books had been removed from the rankings. One petition has drawn more than 22,000 signatures.

(c) 2009 AFP