As Washington scrambled to calm the outrage, Condoleezza Rice, the US Secretary of State, promised an inquiry and punishment for any proven offenders. But at Friday prayers in the Muslim world many preachers demanded vengeance and afterwards thousands took to the streets, burning American flags.

Although the original report in Newsweek was small, it was re-broadcast by television networks such as al-Jazeera and al-Arabiya and in Pakistan it was quoted by Imran Khan, the cricketer-turned-politician, at a press conference. He said it would strengthen the impression that America’s War on Terror was against Muslims.

The most violent protests were in Afghanistan, where the death toll in clashes between demonstrators and security forces reached fourteen after a third day of rioting. Three people were killed and twenty-two injured near Faizabad, in Badakhshan province, when a thousand rioters burnt down aid agencies’ offices.

Worshippers in Pakistan poured on to the streets after prayers, chanting “Death to America”, and burning American flags. In Jakarta, hundreds gathered noisily at a mosque. Thousands marched through the streets of a Palestinian refugee camp in Gaza.

The unrest began this week after Newsweek published an allegation that American military interrogators had desecrated the Islamic holy book in an effort to rattle detainees at Guantanamo Bay in Cuba. The report said that they had placed the Koran on the lavatory inside inmates’ cells and had “in at least one case, flushed a holy book down the toilet” .

The report was condemned by the Pakistani Government, and Khurshid Kasuri, the Foreign Minister, demanded an apology and severe punishment for any soldier found guilty. Hardline Islamic groups said that they would hold protests but before that could happen violent protests erupted in Afghanistan.

Significantly, Saudi Arabia, a key US regional ally which is usually slow in speaking out, became the first Arab state to comment officially yesterday, expressing “deep indignation” and calling for a quick investigation and for the perpetrators to be punished.

The report was denounced initially by the US chargé d’affaires in Kabul and then by the Pentagon and the State Department. As unrest gathered pace, Dr Rice issued an appeal: “I want to speak directly to Muslims in America and throughout the world. Disrespect for the Holy Koran is not now, nor has it ever been, nor will it ever be, tolerated by the United States. Disrespect for the Holy Koran is abhorrent to us all.

“There have been recent allegations about disrespect for the Holy Koran by interrogators at Guantanamo Bay and that has deeply offended many people. Our military authorities are investigating these allegations fully. If they are proven true, we will take appropriate action.

“Guaranteeing religious rights is of great personal importance to the President and to me. During the past few days, we have heard from our Muslim friends around the world about their concerns on this matter. We understand and we share their concerns.

“Sadly, some people have lost their lives in violent demonstrations. I am asking that all our friends around the world reject incitement to violence by those who would mischaracterise our intentions.”

The riots in Afghanistan were the worst displays of anti-US sentiment since the fall of the Taleban in 2002. Four protesters were shot dead on the second day of demonstrations in Jalalabad, a stronghold of the rebel commander Gulbuddin Hekmatyer, and at least three others died in protests the next day. Aid offices were attacked in the capital, Kabul, and more people died yesterday when protests spread to Ghazni and Badakhshan.

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