KANDAHAR: A suicide bomber rammed his explosives-laden car into a convoy of foreign troops in southern Afghanistan on Wednesday, killing four civilians, officials said, adding there were no confirmed military casualties.

About 15 by-standers were also injured in the attack on Nato-led forces travelling on a main road near the police headquarters in Lashkar Gah, capital of the volatile province of Helmand.

“The target of the suicide car bomber was a convoy of foreign troops passing from a crowded area in Lashkar Gah city,” the provincial governor's spokesman, Omar Zwak, told Reuters.

Two men, a woman and a child, all Afghan, were killed and 15 people were wounded, he said.

A police official said there were foreign casualties, but Nato's International Security Assistance Force (Isaf) did not immediately provide any information on the attack or provide confirmation.

About 87,000 Nato-led troops are deployed in Afghanistan to fight an insurgency that erupted after the Taliban regime was ousted from power in 2001.

Foreign troops are withdrawing from the battlefield as Afghan security forces step up to take responsibility for thwarting the Taliban, who are strongest in the southern provinces of Helmand, Kandahar and Uruzgan.

Afghan and international leaders are also trying to seek a peace deal with the Taliban to halt the 12-year conflict before a presidential election in April and the departure of all Nato combat troops by the end of the year.

No group immediately claimed responsibility for Wednesday's attack.

According to a recent United Nations report, civilian casualties in the Afghan war rose 23 per cent in the first half of this year due to Taliban attacks and increased fighting between insurgents and government forces.

Elsewhere in Afghanistan, four drivers were killed and 40 trucks set ablaze when a rocket was fired at a parking lot in Farah province.

The provincial spokesman blamed the Taliban.