A suicide bomber struck at the heart of NATO's operation in Kabul on Saturday, killing at least six Afghan civilians in an attack that officials blamed on the Haqqani network — a militant group the U.S. has designated a terrorist organization.

The blast, which left a bloody stain on a sidewalk just outside the sprawling headquarters of the U.S.-led military coalition, came as a senior Haqqani commander interviewed by The Associated Press vowed revenge for Washington's decision.

The Obama administration gave the Pakistan-based Haqqani network, which is linked to the Taliban, a terrorist label on Friday despite misgivings the move could further stall planned Afghan peace talks.

The commander said the Haqqani network's military commander, Sirajuddin Haqqani, wants to carry out "80 to 100 attacks on U.S. forces in Afghanistan and 20 attacks on other NATO members" in retaliation for the terrorist declaration.

No coalition casualties were reported in Saturday's blast, German Brig.-Gen. Gunter Katz, the NATO spokesman, said.

But the insurgents' continued ability to strike so close to NATO headquarters has undermined coalition claims of improving security as foreign troops withdraw and hand over security responsibilities to Afghan forces across the country by the end of 2014.

The heavily fortified Afghan capital has experienced a series of attacks that are particularly valuable because they score propaganda points for the insurgents by throwing doubt on the government's ability to provide security even in its own seat of power.

The bomber, who Kabul police estimated to be about 14 years old, struck just before noon on a street that connects the alliance headquarters to the nearby U.S. and Italian embassies, a large U.S. military base and the Afghan Defence Ministry.

He detonated his explosives while walking down the street, according to Kabul police. The Ministry of Interior said some of the victims were street children.

The blast occurred just a few hours after hundreds of Afghans and officials had gathered a few hundred meters (yards) away to lay wreaths at a statue to commemorate the 11th anniversary of the death of Ahmad Shah Massoud.

The charismatic Northern Alliance commander was killed in an al-Qaida suicide bombing two days before the Sept. 11, 2001, terrorist attacks in the U.S. The alliance joined with the United States to help rout the Taliban after America invaded Afghanistan a month later.

Interior Ministry spokesman Sediq Sediqi blamed Saturday's attack on the Haqqani network, one of the most dangerous militant groups fighting international troops in Afghanistan. He did not say how he came to that conclusion, but the Haqqani group has been responsible for several other high-profile attacks in the Afghan capital.

The Taliban claimed responsibility for the attack, saying the target was a "clandestine CIA-run headquarters" nearby. Taliban spokesman Zabiullah Mujahid said the explosion was carried out by a 28-year-old fighter from Logar province, south of Kabul.

The Haqqani commander, who spoke to The Associated Press on condition of anonymity because he feared being targeted if identified, also said the Taliban were responsible for Saturday's attack.

The terrorist designation bans Americans from doing business with members of the Haqqani group and blocks any assets it holds in the United States. American officials estimate the Haqqani forces at 2,000 to 4,000 fighters and say the group, which is based in Pakistan, maintains close ties with al-Qaida.

The Haqqani commander said the decision would hamper efforts to restart peace discussions. He called the U.S. hypocritical, saying it labeled the group a terrorist organization even though U.S. officials reached out to the Haqqani network last year in hopes of holding peace talks.

In a separate statement, Mujahid also said the U.S. terrorist label would only embolden fighters to battle foreign troops.

The Haqqani commander and Mujahid also both said the Haqqani network is not separate from the Taliban and follows the orders given by Taliban leader, Mullah Mohammed Omar.

Mujahid added that the Taliban did not have any trade agreements with any American companies or individuals or any monetary funds in the United States that could be frozen. He said the terrorist designation was indicative of the United States' "complete defeat and dismay" in Afghanistan.

The Haqqani network has been blamed for a series of high profile attacks against foreign targets in Kabul, including co-ordinated attacks last April against NATO and government facilities that lasted more than a day before the insurgents were killed. A year ago, they were blamed for a rocket-propelled grenade assault on the U.S. Embassy and NATO headquarters. In June, gunmen stormed a lakeside hotel near Kabul and killed 18 people in a 12-hour rampage.