Police say at least four civilians have been killed and more than 20 wounded by a powerful suicide car bomb in the Afghan capital, Kabul. (Reuters)

Police say at least four civilians have been killed and more than 20 wounded by a powerful suicide car bomb in the Afghan capital, Kabul. (Reuters)

A suicide bombing killed at least four people, including a woman and two children, and wounded more than 20 on a major commercial boulevard in the Afghan capital just before midday Sunday, police officials and witnesses said.

The attack, apparently carried out by Taliban insurgents, was aimed at a convoy of NATO forces, but Afghan and NATO officials said no foreign forces were killed or injured. Witnesses said a car swerved between two armored vehicles in the convoy and detonated.

U.S. Lt. Col. Christopher Belcher, a spokesman for NATO forces in Kabul, confirmed that there had been an attack on a NATO convoy in Kabul and said no international forces had been harmed. He said he could not provide any further details.

The blast left blood and body parts scattered across several blocks. Several civilian vehicles were burned, and at least two NATO vehicles were damaged. At a glass-fronted commercial building close to the blast site, every sheet of glass was shattered. Sunday is a busy working day in Afghanistan.

A spokesman for the Taliban, Zabiullah Mujahid, asserted responsibility for the attack in tweets in English to journalists. He said the attacker, Anwar Khan, had destroyed two NATO tanks and killed eight foreign “occupiers” inside. He said Khan had been “martyred” while carrying explosives in a hatchback vehicle.

Afghan shopkeepers remove broken glass and debris at the site of a suicide attack in Kabul August 10, 2014. A suicide car bomber targeted a convoy of foreign forces in the capital Kabul on Sunday, killing at least four Afghan civilians, including children, and wounding dozens, Afghan security officials said. (Omar Sobhani/Reuters)

Barat Ali, a man in his mid-20s who worked in a bakery on the block, said he and his co-workers hid after hearing a “very strong explosion.” When they came out, he said, they saw thick smoke rising. All the bakery windows were broken, and one worker was wounded.

Another witness, Noorullah, who owns a shop in the area, said he saw the suicide bomber’s vehicle, a black Corolla, with a headless man in the driver’s seat.

Taliban insurgents have staged numerous attacks in recent weeks, both in the capital and in various provinces, in what Afghan and NATO officials have described as a strategy to test the resistance of Afghan defense forces as U.S. and NATO troops continue to withdraw.

The attack came two days after Secretary of State John F. Kerry visited Kabul to encourage two rival presidential candidates to accept a ballot recount from a fraud-marred June 14 runoff election and form a joint government as soon as possible. The United States is waiting for a new Afghan president to sign a bilateral security agreement that will allow some U.S. troops to remain in the country after the pullout of combat forces at the end of the year.