KABUL, Afghanistan -- A suicide bomber on foot penetrated one of the most closely defended parts of Kabul on Saturday, blowing himself up outside a carpet shop a few hundred yards from international embassies and the walls of the NATO headquarters and killing at least six Afghan civilians, including some children.
The bombing punctuated a tense holiday in commemoration of a mujahedeen commander, killed in 2001, for which security had already been increased in Kabul. Clashes between his supporters and other ethnic groups and the police in a Kabul neighborhood left cars tipped over and on fire, police guard posts burning and at least two dead, an indication that ethnic tensions remain combustible here.
The blast did not kill any foreigners or harm NATO installations. But it showed the insurgents' ability to reach inside the central district only a few hundred yards from the United States Embassy, the presidential palace and NATO compounds.
The Taliban claimed responsibility, saying the target was a nearby Central Intelligence Agency installation.
Asked whether the bombing had been directed at a C.I.A. property, Jamie Graybeal, a spokesman for the International Security Assistance Force, the formal name of the NATO-led military coalition, said, "We do not feel it appropriate to talk about what the Taliban was trying to target."
The Interior Ministry said six people were killed in the attack, and four others were wounded. But at the scene of the bombing, the bodies of six children and two adults lay sprawled beneath trees on the side of the road opposite the Spanish Embassy and the residence of the Indian ambassador. Among the dead children were two sisters.
Witnesses said the number of deaths could be even higher. The police took away some victims soon after the attack, said Abdul Jamil, 38, a resident. "I saw about 12 bodies, all were civilians," he said. "I saw a little girl whose legs were blown away in the back of the police truck."
The explosion rocked the center of the capital around 11:30 a.m. Gen. Daoud Amin, the Kabul deputy police chief, said the attacker had approached on foot carrying a backpack. Street vendors, many young children who easily pass the many checkpoints, typically bring scarves, hats and other merchandise in sacks to sell to foreigners near the NATO base and embassies.
General Amin and other officials said the attacker was a boy, 12 to 15 years old. They pointed to severed legs on the street, which they said were those of the bomber. The American Embassy and ISAF both issued statements condemning the use of a teenager to carry out the attack.
But the Taliban said the assailant was 28 and from Logar Province. "Conducting such a successful attack on an important C.I.A. center in Kabul City is something that a 12-year-old boy is not able to do," said Zabiullah Mujahid, a Taliban spokesman.
The attack came a day after the United States designated a Taliban affiliate, the Haqqani network, as a terrorist group. The Haqqanis have carried out attacks in Kabul.
A NATO official in Kabul said the coalition did not yet know whether the Haqqanis were responsible. "I don't think you can link the two," the official said, referring also to the terrorist designation. He asked not to be identified because the investigation was still under way. But a spokesman for the Ministry of Interior, Siddiq Siddiqi, said in a Twitter message that he thought the Haqqanis were behind the attack.
Even as the bomber struck Kabul, former warlords who fought the Soviets and the Taliban in the 1980s and 1990s gathered to commemorate the 11th anniversary of the death of the former mujahedeen commander Ahmed Shah Massoud, who is considered a national hero by many here.
At a time when the American-led coalition is trying to oversee a peaceful transition to full Afghan control, the warlords, including some in the government, joined a meeting of about 1,000 officials in Kabul to urge former mujahedeen fighters to take up arms against the Taliban.
"If the Afghan security forces are not able to wage this war then call upon the mujahedeen," said Marshal Muhammad Qasim Fahim, the first vice president.
Another former warlord who addressed the meeting, Abdul Rab Rassoul Sayyaf, said the government no longer inspired respect and fear, and urged officials to be tougher. "You can't achieve peace and security through pleading and begging," he said.
To tamp down potential frictions, the Ministry of Defense had warned supporters of Mr. Massoud, an ethnic Tajik from the Panjshir Valley who was assassinated by the Taliban in 2001, against parading through the streets with flags and portraits.
But on Saturday long convoys of armed supporters drove through Kabul, and Mr. Massoud's portrait adorned taxis and buildings. An angry crowd converged on Massoud Circle, a landmark in front of the American Embassy, some brandishing AK-47s and harassing passers-by.
"I am so sad today since our leader was martyred 11 years ago this day," said one young man, who gave his name as Zubair.
In a Hazara neighborhood in western Kabul, thousands of Hazara protesters were pushed back by hundreds of police officers, and the police said at least two people had been shot, including a police officer. The protests were touched off after a pro-Massoud convoy of about 50 people hit a car, General Amin said.
The protesters burned down a police checkpoint, he said.
A resident, Ali Yawar, said most of the Massoud supporters had pistols and rifles. "When the police tried to mediate, the mob attacked the police," he said.
Mr. Yawar said as many as five people were killed in the unrest. Many of the deaths were the result of indiscriminate police shooting, he said.
Sangar Rahimi and an employee of The New York Times contributed reporting.
This article originally appeared in The New York Times.