A suicide car bomb aimed at a NATO convoy in southern Afghanistan killed at least 20 civilians on Thursday (August 3), a provincial police chief said. The attack in the Taliban stronghold of Kandahar province occurred southwest of its capital, near where two separate roadside bombs killed a Canadian soldier and injured four more earlier in the day. A NATO spokesman in Kabul said he had heard of the bombing, but had no immediate information on any armed forces casualties. The attack, just days after NATO took over security from U.S. forces in the increasingly volatile south, is the bloodiest caused by a suicide bomber targetting civilians in Afghanistan for months. Four NATO soldiers, including three Britons, have been killed since Monday, when the group took over security for the south in the biggest ground operation in the alliance's history. Six other NATO soldiers have been killed in recent months as the alliance stepped up its deployment ahead of the takeover. The Taliban, intensifying operations in recent months, have vowed to topple President Hamid Karzai's U.S.-backed government and drive out foreign forces. NATO's expansion into the south is aimed at allowing the United States to cut the size of its forces in the country. Afghanistan is going through its bloodiest phase since the Taliban was ousted in 2001, with most of the violence in the south and east, where more than 1,700 people including militants, civilians, aid workers, security forces and more than 70 foreign soldiers have been killed this year alone. Separately, 22 Taliban guerrillas were either killed or wounded in an operation by Afghan police on Wednesday in southern Helmand province, an interior ministry spokesman said.