Four Afghan civilians and a Nato soldier have been killed in two attacks in Afghanistan.

A suicide car bomber struck a convoy of foreign troops near the US embassy in Kabul, killing four civilians, the Afghan government said.

Another 20 people, all of them civilians, were wounded in the blast which took place while a military convoy was passing

The attack happened on a road, close to a traffic junction with access to the US embassy and the health ministry.

"All embassy staff are accounted for," said US embassy spokesman Mark Stroh. Most embassy staff were off work for the US Thanksgiving public holiday.

Separately, a roadside bomb killed one soldier from the Nato-led force and wounded a few others in the southern province of Uruzgan, an alliance official said. He did not give the identity of the victims.

Doubts about the prospects of stability in Afghanistan have increased with violence hitting its worst level this year since the Taliban's removal despite the increasing number of foreign troops.

After a string of suicide attacks in Kabul last year and this year, including a July attack on the Indian embassy that killed 58 people, police have blocked off a number of roads in the capital and introduced more security checks.

While violence has steadily increased across the rest of the country, there have been fewer attacks in Kabul this year, though those that have occurred have struck more high-profile targets.

Meanwhile, a man believed to be a French aid worker recently kidnapped in Afghanistan has appeared in a video with two guns pointed at his head.

The distressed man, who identifies himself on the tape as Dan Egreteau, is seen sitting on the floor pleading for his life and for a ransom to be paid.

He was captured by gunmen in Kabul on November 3 as he drove to work with another aid worker, who managed to escape. An Afghan who tried to prevent the kidnapping was killed.

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