The deaths come just eight days after another three Canadian soldiers were killed in Arghandab by a roadside bomb.

Canada has a 2,750-strong force in southern Afghanistan and on Thursday Ottowa said its mission in Afghanistan would last until 2011.

Robert Gates, the US secretary of defence, suggested during a visit to Kandahar that he would welcome an extension from Ottawa.

But Canada's Parliament "has decided that our mission there ends in 2011," said Dan Dugas, spokesman for Peter MacKay, the Canadian defense minister.

While campaigning in the October legislative elections, Stephen Harper, the Canadian prime minister, said Canada did not agree to a further extension of the Canadian mission beyond 2011.

There are some 65,000 international troops in Afghanistan, including more than 30,000 from the US, struggling to combat worsening violence in the country.