MAZAR-E-SHARIF, Afghanistan >> While it is still too early to say who were the killers of the seven U.N. employees here last week, senior police officials say they suspect current or former Taliban members or other insurgents of leading the violence, aided by sympathizers and hard-line mullahs who whipped up a crowd of thousands angered by a Quran burning in the United States.

Whether the killings were planned, the violence has proved to be a disturbing gauge of the depths of Taliban influence in this progressive northern city, which has always been friendly to the foreign intervention, and of the apparent potential of the Taliban to foment unrest.

Perhaps most unsettling for Western and Afghan officials, former Taliban fighters who were supposed to have switched loyalties as part of an U.S.-financed program were among those who snatched weapons from the guards, police officials said. Three who were living under police protection just a few blocks from the ransacked U.N. compound have been arrested.

That former Taliban fighters may have been involved raises serious questions about the U.S.-backed reintegration program, which is an important element in the strategy to wean Taliban fighters from the insurgency and for President Hamid Karzai to forge peace.

Fewer Taliban members than envisioned have taken advantage of the program, which has received $50 million in U.S. financing. Even for those who have, the violence shows, getting them to change sides may be easier than changing their minds.

It is just one of many quandaries raised by the deadly events that began with protests against the burning of a Quran by the pastor Terry Jones in Florida but ended with a mob killing three U.N. staff members — a Swedish human rights officer, a Norwegian pilot and a Romanian political officer — and four Nepalese guards. Five Afghan civilians also were killed when the police fired on the crowd, and 20 were wounded.

“One day we will have to analyze why the protests only took place in Afghanistan,” said Staffan de Mistura, the head of the U.N. mission in Afghanistan.

The United Nations and Karzai have ordered their own inquiries alongside the police investigation. The police are still questioning 21 people, some of whom admitted their involvement in the violence and some of whom were witnesses, police officials said.

While still blaming the American pastor for inciting the violence, de Mistura called on Friday for the killers to be brought to justice. “There is no justification, no excuse, no possible reason for anyone to have done that horrible act, and therefore they should be found and punished,” he said.

Three former Taliban fighters were detained on the evening of the protests in the government-run safe house where they were living under police protection. One of the men returned with a Kalashnikov rifle that he had seized from an Afghan guard working for the United Nations and has admitted to firing four magazines of bullets, the provincial police chief, Gen. Esmatullah Alizai, said.

There were 19 former fighters from across northern Afghanistan living in the safe house until the protests. The other 16 have disappeared, according to the police guarding the house.

It is clear that the government was caught off guard by the violence and that the police were ill-prepared to contain the large crowd — the two top police officials were at a conference in Kabul. Radical mullahs and students misled the government about the plans for the demonstration and changed the approved route, police officials said.

Taliban or other insurgent or criminal elements in this northern city — usually one of the most peaceful and secure in the country — were able to leverage the high emotions of the crowd, police officials said. People loyal to the renegade insurgent leader Gulbuddin Hekmatyar also had a hand in organizing the protests, one intelligence official said.

In recordings of speeches at a rally before the attack, speaker after speaker — clerics and students — call for jihad and death for infidels and Jews. A resolution drawn up by some of the protest organizers claimed that hundreds of Qurans had been burned in America.

Religious leaders intended to show their strength, each leading followers from mosques around the city to swell the demonstration to 3,000 to 4,000 people, and then encouraging a charge toward the U.N. compound, police officials said.

“It was a political action firstly, and then they used the people’s emotions to get there,” said Gen. Daud Daud, who as police commander of the northern zone oversees security in nine northern provinces. As is common in Afghanistan, he uses only one name. The general vowed to find those responsible and put them on public trial.

Protesters filled the inner courtyard of Mazar’s exquisite blue-tiled shrine to listen to two hours of speeches after Friday Prayer. “You should stand against the infidel,” urged one mullah in a white turban. “Some can stand by the pen; some people can speak against the enemy.”

He broke into Arabic and then translated: “The Prophet says not just the mullah should stand against the infidel; everyone should stand against them.”

A medical student and a theology lecturer from Balkh University put in the original request for permission to hold a demonstration, which they said would be small and peaceful, Alizai said. Their plan, which was approved by the governor and the deputy police chief, was to gather a demonstration at the shrine and then march west past the site of a new U.S. Consulate.

But because it is still under construction and not yet open, the organizers, including the leader of the provincial council, changed the plan at the last minute to march south to the U.N. compound. They called the deputy police chief, who reluctantly agreed to the change since his men were deployed along the western route.

“We learned that nine people got together inside the mosque and made the decision to march to the south,” Alizai said.

The crowd was far bigger than the police had expected and surged through the western gates as soon as they were opened, he said. “They were running like a flood, and the police were confused,” he said. “If we left the American Consulate they might come there,” he said.

The small unit of policemen at the U.N. compound was soon overwhelmed by the crowd, as were the guards, who were under orders not to fire on civilians.

© 2011 The New York Times Company