Afghan roadside bombing kills women, children (CBS/AP) KABUL, Afghanistan - Afghan officials say a mine laid in a road has killed eight civilians in the country's south, including women and children. The governor's office in Helmand province says the eight were driving Monday in Musa Qala district when their car hit the explosives. The United Nations says 579 civilians were killed in the first four months of this year. Militants are responsible for most of these casualties. In the first four months of this year, anti-government forces caused 79 percent of all civilian casualties and Afghan and foreign forces 9 percent. It was not clear who was responsible for the remaining 12 percent. Special Section: Afghanistan, The Way Forward Afghans in uniform kill U.S. serviceman Fallen soldiers' families: War's other casualties The blast comes a day after the latest likely case of an insider attack. An American service member was killed and several others injured Monday when individuals dressed in Afghan police uniforms turned their guns on them in southern Afghanistan, U.S. officials said. In other violence around the country, a senior police official in Kandahar province tells CBS News that seven militants armed with small arms, rocket propelled grenades and some wearing suicide vests attacked a U.S. outpost in the Shahwali Kot district. He said the attack was repelled after an hour-long gun battle and all the attackers were killed outside the parameter of the base. He added that one civilian contractor was killed and a number of soldiers were injured in the attack. The nationalities of the injured soldiers and the slain contractor were not immediately clear. U.S. troops are usually stationed alongside Afghan counterparts at such bases.