MAZAR-I-SHARIF, Afghanistan — The burning of the Muslim holy book by a Florida pastor last month went largely unnoticed in the United States. But it enraged a mob that stormed U.N. offices in a normally placid area of Afghanistan, an outbreak of violence that also signaled broadening anti-American sentiment and the difficulty of handing security responsibility back to Afghans.
Stirred up by three angry mullahs who urged them to avenge the burning of a Koran at the Dove World Outreach Center in Gainesville, thousands of protesters overran the compound of the United Nations in Mazar-i-Sharif on Friday, killing at least 12 people.
The dead included at least seven U.N. workers — four Nepalese guards and three Europeans. Early reports, later denied by Afghan officials, said that at least two of the dead had been beheaded. Five Afghans were also killed.
Swedish Foreign Minister Carl Bildt said Joakim Dungel, a 33-year-old Swede who worked at the U.N. office, was among those killed.
A Norwegian Defense Ministry spokeswoman, Maj. Heidi Langvik-Hansen, said Lt. Col. Siri Skare, a 53-year-old female pilot also died in the attack.
U.N. peacekeeping chief Alain LeRoy said that the other European victim was a citizen of Romania and that a number of U.N. personnel were injured and were being evacuated.
The attack was the deadliest for the United Nations in Afghanistan since 11 people were killed in 2009 when Taliban suicide bombers invaded a guesthouse in Kabul. It also underscored the latent hostility toward the nine-year foreign presence here, even in a city long considered to be among the safest in Afghanistan.
Unable to find Americans on whom to vent their anger, the mob turned instead on the next-best symbol of Western intrusion — the nearby U.N. headquarters.
"Some of our colleagues were just hunted down," said Kieran Dwyer, a spokesman for the U.N. Assistance Mission in Afghanistan.
In Washington, President Barack Obama issued a statement strongly condemning the violence against U.N. workers. "Their work is essential to building a stronger Afghanistan for the benefit of all its citizens," he said. "We stress the importance of calm and urge all parties to reject violence."
The statement made no reference to the Florida church or the burning of the Koran.
Afghanistan, deeply religious and reflexively volatile, has long been one of the most reactive flashpoints to perceived insults against Islam. When a Danish cartoonist lampooned the prophet Mohammed, four people were killed in riots in Afghanistan in 2006. The year before, a one-paragraph item in Newsweek alleging that guards at Guantanamo had flushed a Koran down the toilet set off three days of riots that left 14 people dead.
Friday's episode began when three mullahs, addressing worshipers, urged people to take to the streets to agitate for the arrest of Terry Jones, the Gainesville pastor who oversaw the burning of a Koran on March 20.
Otherwise, said the most prominent of them, Mullah Mohammed Shah Adeli, Afghanistan should cut off relations with the United States.
"Burning the Koran is an insult to Islam, and those who committed it should be punished," he said.
The crowd — some of its members carrying signs reading "Down with America" and "Death to Obama" — poured into the streets and swelled. Gov. Atta Muhammad Noor of Balkh province, of which Mazar-i-Sharif is the capital, later put the number at 20,000.
The victims were killed by weapons that the demonstrators had wrestled away from the U.N. guards, Noor said.
Jones caused an international uproar by threatening to burn the Koran last year on the anniversary of the terror attacks of Sept. 11, 2001. Among others, the overall commander of forces in Afghanistan, Gen. David H. Petraeus, had warned at that time that such an action could provoke violence in Afghanistan and could endanger U.S. troops. Jones subsequently promised not to burn a Koran, but he nonetheless presided over a mock trial and then the Koran burning, with only 30 worshipers attending.
The act drew little response worldwide but provoked condemnation in this region, where it was reported in the local media and where anti-American sentiment already runs high. Last week, President Asif Ali Zardari of Pakistan condemned the burning in an address before Parliament, and President Hamid Karzai of Afghanistan on Thursday called on the United States to bring those responsible for the Koran burning to justice.
Similar sermons set off angry demonstrations in Kabul and Herat, but neither of those boiled over into large-scale violence.
Many in the Kabul crowd were angry, excited young men. One, a 26-year-old student who gave only the name of Samiullah, said the protesters had come to raise their voices against what he called a "wicked act of blasphemy."
Jones was unrepentant.
"We must hold these countries and people accountable for what they have done as well as for any excuses they may use to promote their terrorist activities," he said. "Islam is not a religion of peace. It is time that we call these people to accountability."
In part because of the relative calm in recent years, Mazar-i-Sharif was designated last month by Karzai as among the first major cities in which Afghan forces would take the lead in providing security. That process, to be expanded to other parts of the country by 2014, is a cornerstone of the strategy for U.S. and other Western forces to eventually pull out of Afghanistan.
After taking office, Obama increased U.S. troop levels twice in an effort to stop a resurgence by the Taliban. They now make up about two-thirds of the 150,000 NATO troops in Afghanistan. U.S. military officials say they will start withdrawing some forces in less than four months.
In other developments in Afghanistan, six U.S. soldiers were killed in a single operation in the country's east Wednesday and Thursday, a spokesman for the international coalition said Friday.
The governor of Kunar province, Said Fazlullah Wahidi, said the operation began Wednesday as a joint Afghan and U.S. air and ground operation in the districts of Sarkani and Marawara, close to the border of Pakistan. He said that 14 insurgents were killed and 10 were wounded, but he had no information about casualties among Afghan forces.
Information from the New York Times and Los Angeles Times was used in this report.