KABUL, Afghanistan-- Protesters threw rocks and police shot back Friday as violent anti-U.S. protests spread to more Afghan cities, leaving at least eight people dead and threatening a security crisis for the government.

In neighboring Pakistan, street protests fizzled despite tough rhetoric from hard-line preachers over allegations that U.S. anti-terrorism interrogators desecrated Islam's holy book. The rest of the Muslim world was mostly quiet, with only small rallies at a Palestinian refugee camp and in Indonesia.

Afghan officials suggested opponents of the country's painstaking democratic rebirth were stirring up this week's trouble, while the U.S. government appealed for calm and stressed that the desecration charge was being investigated by the Pentagon.

U.S. Secretary of State Condoleezza Rice said that if the allegations "are proven true, we will take appropriate action. Respect for the religious freedom for all individuals is one of the founding principles of the United States."

Friday's deaths -- reported in four Afghan towns and cities -- brought to 15 the number of people killed in the biggest outpouring of anti-American sentiment since a U.S.-led military campaign drove the Taliban regime from power at the end of 2001.

Afghan officials said some of the protesters chanting anti-American slogans and stoning the offices of international relief groups are being encouraged by factions that have resisted U.N. disarmament drives or been sidelined by President Hamid Karzai's government.

"This is organized by particular groups who are the enemies of Afghanistan," Interior Ministry spokesman Latfullah Mashal told The Associated Press. "They are trying to show that the situation -- that security -- is not good."

Sibghatullah Mujaddedi, an Islamic cleric and close ally of Karzai, told worshippers in Kabul's main mosque Friday that the violence was against Islam.

"The ones who are here to help us and help our government, until they leave our country, we should respect them," Mujaddedi said.

He claimed "foreign hands" were stirring the violence -- words often used to accuse Pakistan, where leaders of the Taliban and the Hizb-e-Islami group led by Gulbuddin Hekmatyar are believed to find refuge.

Shooting broke out in the southeastern city of Ghazni as protesters swarmed toward a police station and the governor's residence after Friday prayers, chanting "Death to America" and pelting the buildings with rocks, witnesses said.

Shafiqullah Shafaq, a doctor at the city's hospital, told AP that two civilians and a police officer were fatally shot and 21 people were wounded, including the provincial police chief.

In northeastern Badakhshan province, three men died when police opened fire trying to control hundreds of protesters in Baharak district, Gov. Abdul Majid said. Twenty-two people were reported hurt, including three police officers.

Majid said the crowd set fire to the offices of a British aid group and Focus, a reconstruction agency financed by the Aga Khan Foundation, a fund set up by the spiritual leader of the world's 20 million Ismaili Muslims.

Officials said a protester was killed when police fired during a riot after prayers in the northwestern town of Qala-e-Naw and another died from a gunshot wound in Gardez, near the Pakistani border.

The protests began after Newsweek magazine reported in its May 9 edition that interrogators at the U.S. Navy base 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 arrested during the U.S.-led war against the Taliban and its al-Qaida allies in Afghanistan.

Protests over the Newsweek report erupted Tuesday in the eastern city of Jalalabad, and the killing of four rioters by police further enflamed passions. Demonstrations -- many of them violent -- have occurred in at least 12 Afghan towns and cities.

Saudi Arabia joined fellow U.S. ally Pakistan in registering dismay over the allegations, as did the 57-nation Organization of the Islamic Conference and Egypt's Muslim Brotherhood, a banned militant religious movement.

But aside from Afghans, few in Muslim lands have taken to the streets.

Some 1,500 activists from the Islamic militant group Hamas staged an anti-U.S. protest Friday in the Gaza Strip, chanting "Protect our holy book." About 50 people demonstrated in the eastern city of Makassar in Indonesia, the world's most populous Muslim country.

An appeal by Pakistan's opposition Islamic coalition Mutahida Majlis-e-Amal for Muslims to protest after Friday prayers fell flat. Only a few hundred people turned out for peaceful demonstrations in Islamabad, Lahore and Peshawar.

"By insulting the Quran, they have challenged our belief. We are hurt ... If we don't rise against Americans, if we don't give them a strong message today, they will do it again," cleric Hafiz Hussain Ahmad told worshippers at a mosque in Islamabad, the Pakistani capital.