A car bomber has hit a Canadian military convoy in a southern Afghan city, killing a senior Canadian diplomat, two civilians and wounding 13 others, officials said.

A purported Taliban spokesman, Qari Mohammed Yousaf, called The Associated Press and claimed responsibility for Sunday's bombing, warning that "these attacks will continue for a long time. We have many more suicide attackers ready to go".

"We will continue this strategy until all foreign forces leave Afghanistan," he said.

Sunday's attack occurred as the convoy was driving near the Canadian base in Kandahar city, a former Taliban stronghold, said Interior Ministry spokesman Dad Mohammed Rasa. At least two civilians were killed and 10 were wounded, he said.

Lieutenant-General Marc Dumais, Canada's deputy chief of defence, said Glyn Berry, a senior foreign affairs officer and the political director of a reconstruction team in Afghanistan, was killed.

He said three of the 13 wounded are Canadian soldiers and that two are in critical condition.

Paul Martin, the Canadian prime minister, called the attack a "tragic incident" and expressed his condolences to the families of the victims.

Nine Canadians have died in Afghanistan. Four soldiers were mistakenly bombed by a US fighter pilot in 2002 and four others have died in accidents.

The Canadian prime minister said his country's mission in Afghanistan is vital.

Canada has about 650 troops in Afghanistan, nearly all in Kandahar, and Ottawa plans to increase the Canadian military presence in Kandahar to 2,000 next month.

A witness to the attack, shopkeeper Rahim Gul, said he saw a sedan vehicle blow up as it was passing the convoy.

"The explosion was so big. It destroyed one jeep and blew it totally to the other side of the road," he said, adding that he saw at least three wounded soldiers.

Violence spike

Violence across southern and eastern Afghanistan spiked last year, leaving about 1600 people dead.

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