A suicide bomb attack targeting a NATO convoy in southern Afghanistan has killed a soldier and four civilians.

The explosion took place south of the main base in Kandahar where thousands of NATO and US troops are stationed, said Sergeant Jeff Loftin, a spokesman for NATO's International Security Assistance Force.

He was unable to confirm the number of injured beyond saying ‘a few’.

An earlier statement from ISAF said the soldier’s death was caused by an improvised explosive device (IED).

But police and witnesses said the attacker blew up his vehicle on a bridge spanning the main highway from Kandahar city, the spiritual capital of the Taliban, towards the district of Spin Boldak on the border with Pakistan.

The interior ministry said the attacker drove a car bomb into a NATO convoy killing ‘four of our innocent civilian compatriots’.

The nationality of the dead soldier was not given, in line with ISAF policy.

There are about 121,000 international troops based in Afghanistan fighting an insurgency being waged by the remnants of the Taliban, toppled from government in US-led invasion in late 2001.

Monday’s death brings to 102 the number of foreign soldiers to die in Afghanistan so far this year.