"Four civilians driving in the vehicle have been martyred," he said.

There was no immediate claim of responsibility for the blast, which was planted in a busy shopping area.

Attacks and kidnappings linked to an insurgency led by the extremist Taliban movement, which was in government between 1996 and 2001, have increased in and around the city in recent months.

On Saturday a suicide bomber blew himself up among Italian military engineers working on a footbridge in the town of Paghman, 25 kilometres west of Kabul.

One Italian soldier and eight Afghans, three of them children, were killed. The Taliban claimed responsibility. © 2007 Australian Broadcasting Corporation