Pakistan on Monday reiterated its demand for an investigation into the alleged desecration of Islam's holy book at the U.S. prison in Guantanamo Bay (search), despite a Newsweek apology for errors in a report claiming a Koran was flushed down a toilet to rattle detainees.

The story sparked demonstrations across the Islamic world last week, with about 15 people killed during an anti-American protest in Afghanistan.

Pakistan, a key ally in the U.S.-led war on terror, requested Monday that U.S. officials complete a full investigation into the allegations.

"We have asked for a thorough investigation conducted by the U.S. administration and we would expect the results of the official investigation shared with us," Foreign Ministry spokesman Jalil Abbas Jilani (search) told a news conference.

Newsweek reported in its May 9 issue that U.S. military investigators had found evidence that interrogators at the base in Cuba placed copies of the Koran in washrooms and had flushed one down the toilet to get inmates to talk.

Most of the 520 inmates at Guantanamo Bay, Cuba, are Muslims arrested during the U.S.-led war against the Taliban and its Al Qaeda (search) allies in Afghanistan.

On Sunday, Newsweek apologized for errors in its report.

"We regret that we got any part of our story wrong, and extend our sympathies to victims of the violence and to the U.S. soldiers caught in its midst," Newsweek Editor Mark Whitaker (search) wrote in a note to readers.

The White House said Newsweek's response was insufficient.

"The report has had serious consequences. People have lost their lives. The image of the United States abroad has been damaged," White House spokesman Scott McClellan said.

The 22-nation Arab League issued a statement saying if the allegations panned out, Washington should apologize to Muslims.

On Saturday, President Gen. Pervez Musharraf and Prime Minister Shaukat Aziz demanded "exemplary punishment" for those behind the reported desecration. In Afghanistan and Pakistan, insults to the Koran and Islam's prophet, Muhammad, are regarded as blasphemy and punishable by death.

Qazi Hussain Ahmed, a hardline Pakistani Islamist leader and opposition lawmaker, said Sunday that Islamic groups in Pakistan, Egypt, Malaysia, Britain, Turkey and other countries would hold more rallies May 27 to protest the alleged desecration.

Lebanon's most senior Shiite Muslim cleric said the alleged desecration is part of an American campaign aimed at disrespecting and smearing Islam.

Grand Ayatollah Mohammed Hussein Fadlallah urged Muslims and international human rights organizations "to raise their voices loudly against the American behavior, which is hostile to Islam and Muslims."

In a statement faxed to The Associated Press before Newsweek's apology, Fadlallah called the alleged desecration a "brutal" form of torture.

"This act is not an individual act carried out by an American soldier, but rather it is part of the American behavior of intellectual and psychological education in disrespecting Islam and smearing its image in the souls of Americans," Fadlallah said.

On Sunday, U.S. national security adviser Stephen Hadley said in an interview on CNN that the allegations were being investigated "vigorously."

"If it turns out to be true, obviously we will take action against those responsible," he said.