Government officials said six bystanders died in the explosion in the Shah Shaheed residential district in the southeast of Kabul, while the NATO coalition were unable to give details of any casualties.[break]
One NATO sports utility vehicle was completely destroyed in the blast and surrounding streets were cordoned off as US troops arrived at the scene. Schoolgirls fled the area in tears as the clean-up operation began.
"At around 8:00 am (0330 GMT) this morning, terrorists detonated an explosives-packed (Toyota) Corolla car near a convoy of foreign forces," Hashmat Stanikzai, the Kabul police spokesman, told AFP.
Afghan health ministry official Sayed Kabir Amiri said local hospitals confirmed six people had died and 37 were wounded, all of them civilians.
"Some of the bodies are badly damaged and can´t be identified," he added.
Lieutenant Quenton Roehricht, a spokesman for NATO´s US-led International Security Assistance Force, confirmed a coalition vehicles had been targeted in Kabul and said further information would be released shortly.
"I was at home when I heard a terrible explosion and our whole building shook," Mustafa, a young local man, told AFP.
"All our windows are shattered. I rushed outside to bring my little brothers and sisters from school. I saw five or six people covered in blood who were being taken away in police vehicles."
Police added that at least 10 houses had been severely damaged.
It was the first major attack in Kabul since March 9 when a suicide bomber on a bicycle killed nine people outside the defence ministry during a visit by US Defense Secretary Chuck Hagel.
It comes just weeks after the Taliban launched their annual "spring offensive" on April 27, opening a crucial period for Afghanistan as local security forces take the lead in offensives against the insurgents.
The Islamist militants said multiple suicide bombings, "insider attacks" by Afghan soldiers and "special military tactics" would target international airbases and diplomatic buildings to inflict maximum casualties.
All NATO combat missions will finish by the end of next year and the 100,000 foreign troops deployed across Afghanistan have already begun to withdraw from the battlefield.
More than 11 years after the Taliban regime was ousted in 2001, efforts to seek a political settlement ending the violence have so far made little progress, but pressure is growing ahead of the NATO withdrawal.
In the most recent NATO casualties, a roadside bomb killed three US soldiers in the volatile province of Kandahar on Tuesday.
Three Georgian soldiers were killed in neighbouring Helmand province on Monday when a suicide bomber detonated a vehicle laden with explosives.
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