OTTAWA (Reuters) - A Canadian soldier was killed and three others were injured in southern Afghanistan on Friday when a bomb blast hit the armored vehicle they were riding in, the military said. The incident occurred in the Zhari district to the west of the city of Kandahar, where Canada has a 2,700-strong military mission.Canada has now lost 104 troops since the country's military mission to Afghanistan started in late 2002. The soldier was the seventh Canadian member of the armed forces to die in bomb blasts in December alone. The mission is due to end in 2011.