Two Canadian soldiers killed in Afghan blast

(Updates with deaths of soldiers)

OTTAWA, April 11 (Reuters) - Two Canadian soldiers were killed and two wounded in Afghanistan on Wednesday when a roadside bomb exploded near their vehicle, the Defense Ministry said.

The attack happened three days after six soldiers died when their armored vehicle ran over a massive explosive device in the war-torn country. Canada has lost 53 soldiers since troops were sent to Afghanistan in 2002 as part of the U.S.-led war on terrorism.

The Defense Ministry said the blast took place about 23 miles (38 km) west of the southern city of Kandahar -- where Canada has a 2,500-strong mission -- as the soldiers were assisting another vehicle that had been damaged in an earlier bomb attack. One of the survivors had serious wounds.

"Today is another sad day for the Canadian forces and our thoughts and prayers are with the families and friends of these fine soldiers," a ministry statement said.

"The incidents of these last few days, while challenging ... have galvanized our determination to support and help the long-suffering people of Afghanistan."

Opinion polls show Canadians are sharply divided over the wisdom of the mission, which is due to end in February 2009. Opposition politicians say Canada's troops spend too much time fighting Taliban militants and not enough on helping rebuild the country.