San’a, Yemen ? Yemen’s government and thousands of university students on Saturday added their voices to the Muslim world’s anger over alleged desecration of Islam’s holy book, the Quran, by U.S. troops at the Guantanamo detention facility.

The Arab League, based in Cairo, Egypt, also issued a statement saying if the allegations panned out, Washington should apologize to Muslims.

In Afghanistan, where recent protests against the reported desecration left 15 people dead, President Hamid Karzai blamed the violence on opponents trying to tarnish the country’s image. Another U.S. ally, Pakistan’s President Gen. Pervez Musharraf, called for a thorough investigation.

The denunciations follow protests elsewhere in the Middle East and Asia after Newsweek magazine reported that U.S. interrogators at Guantanamo Bay, Cuba, placed Qurans in washrooms to unsettle suspects, and “flushed a holy book down the toilet.”

Many of the 520 inmates at Guantanamo are Muslims.

Secretary of State Condoleezza Rice has promised “appropriate action” would be taken if the allegations are proven true. The U.S. government has said the desecration charge was being investigated by the Pentagon.

The 22-nation Arab League also criticized the alleged desecration of Islam’s holy book.

The Middle East reaction was calm compared to deadly protests in the past three days in the Afghan capital, Kabul, in which 15 people died. Protesters threw rocks, and police shot back in four Afghan cities.