Newsweek has apologized for errors in a story that outraged Muslims, triggering several days of deadly riots.

Newsweek says its report -- containing allegations that U.S. military interrogators defiled a copy of Islam?s most sacred book -- was based on a confidential, single source who now has doubts about the story.

The report in the May 9th issue said U.S. military investigators found that American interrogators at the U.S. detention facility in Guantanamo Bay, Cuba had flushed a copy of the Koran, the sacred Muslim text, down a toilet. Many of the 520 inmates at Guantanamo Bay are Muslims, arrested during the U.S.-led war against the Taleban and al-Qaida in Afghanistan.

After newspapers in Pakistan and Afghanistan ran stories about the Newsweek article, violent anti-American protests erupted in several cities. At least 15 people were killed and several dozen others were injured.  

Newsweek now says its source -- whom Editor Mark Whitaker describes as a "senior U.S. government official" -- is not sure whether the story about the Koran is true.

In a note to readers, Mr. Whitaker said that before Newsweek published the article, it sought comment from two Defense Department officials. He says the one official who did respond did not dispute the Koran charge.

Dan Klaidman is Newsweek's Washington Bureau Chief.  "It is a reminder to all of us that words have consequences and our words have consequences and we need to be mindful of that."

A coalition spokesman in Afghanistan, Colonel James Yonts, said U.S. officials are investigating the allegations, and said the military does not condone any religious persecution of detainees. "Any disrespect to the Koran and any other religion is not tolerated by our culture and our values."

Monday, Muslim leaders in one Afghan province that saw violent protests called on American authorities to investigate the allegations and respond within three days.