KABUL - Afghanistan's powerful vice president, Marshal Mohammad Qasim Fahim, died of natural causes on Sunday, only weeks before the country is due to elect a new leader. He was 57.Once one of Afghanistan's most feared warlords, Fahim had been a top commander in the Northern Alliance, a group of anti-Taliban militia leaders, after the 1992-96 civil war."It is with deep sadness that we learn of the passing away of Marshal Mohammad Qasim Fahim, the First Vice-president of the Islamic Republic of Afghanistan. May his soul rest in peace," President Hamid Karzai's office said, declaring three days of national mourning.The United Nations mission in Afghanistan called Fahim "a good and trusted partner of the UN". Back in 2009, UN officials and diplomats had criticised Fahim's appointment because he was accused of serious human rights abuses. It was unclear what, if any, role Fahim had planned for next month's presidential election. Pictures on local media showed government dignitaries streaming into pay their respects to Fahim, whose body was wrapped in an embroidered gold robe. He fought alongside US troops to defeat the Taliban and was a staunch backer of Karzai, whom he promoted as Afghanistan's interim leader and later served as both defence minister and vice president. Fahim, vice president since 2009, spoke little to the media, said Kate Clarke of the Kabul based thinktank Afghanistan Analysts Network, but wielded great influence in closed door meetings. "Karzai, Fahim and the Americans have been the three key powers in Afghanistan since 2001," she said. "Meanwhile, a roadside bomb ripped through a car in southern Afghanistan, the deadliest of a series of weekend attacks that killed 11 civilians, officials said Sunday.Seven people, including three women and two children, were killed and eight others wounded when the car was hit while travelling in the volatile Helmand province, according to a statement by the provincial governor's office. It said the car was one of two carrying civilians between the districts of Musa Qala and Nawzad. It hit the bomb in Musa Qala.The statement said two other civilians were killed Saturday in a bombing in the Kajaki district, providing no other details. Insurgents also attacked a checkpoint elsewhere in the district, killing an Afghan policeman, it said.The statement said: "Taliban militants regularly plant roadside bombs to target Afghan and NATO forces, but the devices often kill Afghan civilians."Afghan security forces also killed 13 Taliban insurgents in Helmand's Gereshk district, according to the statement.Elsewhere in the south, a bomb exploded near a store Sunday, killing two civilians and wounding two others in the Spin Boldak district of Kandahar province, said Zia Durani, a spokesman for the provincial police chief.