Canadians serving with the 6,100-strong NATO-led International Security Assistance Force (ISAF), were patrolling near a field close to their Camp Julien base in Kabul when a man approached and blew himself up.

"The attack on these soldiers was a shameful act, but it will not detract from our commitment to help Afghanistan build a better, more hopeful future," said the Dutch NATO chief.

"Canadian soldiers are in Afghanistan as part of NATO's contribution to restore peace and security in a country that has been plagued with conflict and violence for decades," he added.

Some 33 countries contribute troops to the ISAF force, which has been led by NATO since last August. NATO has agreed to expand its mandate to beyond Kabul, although it has battled to drum up contributions from alliance member states.

The Kabul attack came one month after the Taliban warned that dozens of suicide bombers, rarely seen in Afghanistan in the past, had infiltrated the Afghan capital intending to attack foreign targets.

WAR.WIRE