KABUL, Afghanistan >> A suicide car bomber attacked a NATO convoy traveling through a crowded neighborhood in Afghanistan’s capital Saturday, killing at least 12 people, including three American civilian contractors for the international military force, authorities said.

The Taliban quickly denied it was behind in the attack in Kabul’s Macrorayan neighborhood, though the militants increasingly have been targeting Kabul in recent weeks and often don’t claim attacks that maim large numbers of civilians.

The attack struck near the private Shinozada hospital, the sound of the powerful blast roaring throughout the capital. Ambulances and Afghan security forces quickly surrounded the blast site, blocking access off from about 1 kilometer (half a mile) away.

The bombing killed at least 11 Afghan civilians and one foreigner and wounded 66, said Wahidullah Mayar, a Health Ministry spokesman. In a statement, NATO said one of the Americans was killed in the blast, while the two others later died of their wounds. The contractors were not named.

It was not immediately possible to reconcile the differing casualty figures, though conflicting information is common after such attacks.

At least one armored vehicle in the convoy had been destroyed by the blast. It wasn’t clear how many armored cars were in the convoy, though it is at least two, often three because of heightened security concerns in the capital.

The blast struck as schools were letting out for the day in Macrorayan, a Soviet-built housing estate lined with shops, hospitals and schools. Najib Danish, a deputy Interior Ministry spokesman, said the attack destroyed more than a dozen civilian vehicles parked in the street and passing by.

"A lot of dead bodies and wounded victims were there after the explosion happened in the area," said Mohammad Hussain, who was wounded in the attack. "There were a lot of casualties."

No group immediately claimed responsibility for the attack. In an email to journalists, Taliban spokesman Zabiullah Mujahid denied his group was responsible.

However, the Taliban has stepped up its assaults on Afghan security forces since U.S. and NATO troops ended their combat mission in the country last year. The militants also have launched a series of attacks in Kabul in recent weeks following Afghan authorities announcing the death of the Taliban’s one-eyed leader Mullah Mohammad Omar. Their targets have included foreign military and civilian convoys.

On Aug. 7, a Taliban attack on a NATO military base near Kabul’s international airport killed an American soldier and eight Afghan contractors. A Taliban-claimed suicide car bombing targeting a NATO convoy on June 30 on the main highway to the Kabul airport wounded two U.S. soldiers and at least 24 others while killing two Afghan civilians.

On May 17, a British security contractor was killed when the armored car he was traveling in for Eupol was hit by a suicide car bomber. Two Afghan women nearby also were killed.