(Adds Interior Ministry, NATO comment, Canadians wounded, Germans attacked)

KANDAHAR, Afghanistan, April 10 (Reuters) - A suicide car bomber in Afghanistan attacked a Canadian military convoy on Thursday killing eight civilians and wounding 22 people, among them three Canadian soldiers, authorities said.

There was no claim of responsibility, but the Taliban have vowed to step up their war to expel foreign troops and bring down the Western-backed government. Intermittent fighting has been picking up recently after a traditional winter lull.

Among those killed in the blast were three children of a roadside vendor, the Interior Ministry said.

Kandahar police chief Sayed Aqa Saqib initially said none of the soldiers in the NATO convoy was hurt as the bomber set off his explosives just after it had passed. But the Interior Ministry later said three Canadian soldiers were wounded.

The NATO-led force, which has 47,000 troops in Afghanistan said three soldiers were slightly wounded but did not give their nationality.

"ISAF troops immediately responded to calls for assistance, airlifting the injured to a hospital for treatment and securing the area," NATO said, referring to its International Security Assistance Force.

Saqib said eight people had been killed but the Interior Ministry said the death toll was five. NATO said it had reports of nine dead. Two policemen were wounded.

Despite the presence of about 60,000 foreign soldiers led by NATO and the U.S. military, as well as 140,000 Afghan troops and police, the Taliban have made a comeback in the past two years and more than 11,000 people have been killed in violence.

Most of the violence has been in the south and east, in ethnic Pashtun areas near the Pakistani border, but attacks have also been taking place in the north and west, which have been generally peaceful.

An armed forces spokesman in Germany said a suicide bomber attacked a German patrol in northern Afghanistan on Wednesday. None of the Germans was killed or wounded. (Writing by Sayed Salahuddin; Editing by Robert Birsel)

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