A Taliban suicide car bomber has killed 12 Afghan civilians and six foreign troops in an attack on a NATO convoy in the Afghan capital Kabul.

A Taliban spokesman said they were responsible for the attack and had used a van packed with explosives.

The interior ministry said 12 Afghan civilians had been killed and 47 others were wounded.

One senior police officer claimed five US and two Canadian soldiers had been killed, while another source said five foreign troops had died. A spokesman for NATO-led forces would not confirm the toll but said a convoy had been attacked.

President Hamid Karzai said that there had been casualties from the NATO-led International Security and Assistance Force, without giving details.

He told a news conference: "A suicide bomber attacked NATO troops that inflicted casualties on both NATO and innocents civilians including women and school children. I condemn this attack on strongest terms and hope that Afghanistan one day gets rid of this."

An increasingly resurgent Taliban announced a spring offensive in May against government officials and foreign forces and diplomats in Afghanistan.