A fierce attack on a military base in southern Afghanistan has killed two soldiers, a Canadian and an American, as a Taliban spokesman said a spring offensive had begun.

"The weather is getting warmer and Taliban attacks on coalition and Afghan forces have begun," said Mullah Mohammad Hanif by telephone from an undisclosed location.

Fighting traditionally picks up in the Afghan spring when snow blocking mountain passes melts.

According to the US military's statement, four other coalition soldiers and an Afghan soldier were wounded in the attack in Helmand province, and about a dozen insurgents were killed.

The attack was in Sangin district, where regular violence linked to Taliban insurgents occurs, about 110km northwest of Kandahar.

Mortars, rocket-propelled grenades and small arms were used, Canada's department of national defence said.

Increasing violence

Violence has intensified in recent months and the Taliban has vowed to unleash a new wave of attacks in its campaign to oust foreign forces and the Western-backed government of Hamid Karzai, the president.

Six Afghan soldiers were killed in Sangin on Tuesday when a bomb struck their vehicle, which burst into flames, said General Rahmatullah Raufi, the army corps commander for the southern region.

Despite the rising level of violence, the US is hoping to trim its force of more than 18,000 troops in Afghanistan by several thousand, while Nato partners, including Britain, Canada and the Netherlands are sending about 6,000 more.

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