4 US troops killed in separate Afghan incidents (AP) KABUL, Afghanistan - An Afghan soldier fatally shot an American service member and a local interpreter in southern Afghanistan, officials said Thursday, the latest in a string of attacks against U.S. and other foreign forces by their Afghan partners. In the east, meanwhile, three U.S. service members were killed in a bomb attack, according to NATO and a U.S. official. The official confirmed the nationalities on condition of anonymity because the information had not yet been publicly released. Further details were not immediately available. In the insider attack in southern Kandahar province, an Afghan soldier opened fire with a machine gun from atop a building, killing a U.S. soldier and an Afghan interpreter and wounding three other coalition service members before he was gunned down, a senior U.S. defense official said. The official spoke on condition of anonymity because he was not authorized to release details. The U.S. military officially confirmed only that a man wearing an Afghan army uniform turned his gun on coalition service members late Wednesday, killing one. The incident was under investigation, the military said. Since the beginning of the year, there have been at least 16 such attacks against American and other international troops. The U.S.-led coalition is trying to mentor and strengthen Afghan security forces so they can lead the fight against the Taliban, and foreign troops can go home by the end of 2014. That mission, however, requires a measure of trust that has been repeatedly undermined by the deaths of coalition troops at the hands of their Afghan partners. In one of the highest-profile attacks, a man working as a driver at the Afghan Interior Ministry shot dead two U.S. military advisers at close range in March. That incident alone led the U.S. military to temporarily pull all its advisers out of Afghan ministries. U.S.-Afghan ties have also been under strain following Quran burnings at a U.S. base and the killing spree allegedly by an American soldier in the south in recent months. Relations appeared to be shifting back on track, with Washington and Kabul agreeing to a long-awaited deal earlier this week on a strategic pact to govern the U.S. presence in Afghanistan till 2024. NATO: Man in Afghan uniform kills coalition troop Losing the media war in Afghanistan The U.S. military chooses its language carefully in describing insider shootings because of the possibility that assailants may be insurgents disguised in Afghan army uniforms and not actual members of the Afghan security forces. Such uniforms are easily available in markets in Afghanistan, and the Taliban have used them to mount previous attacks on international or Afghan military installations. Since 2007, more than 80 NATO service members have been killed by Afghan security forces, according to an Associated Press tally, which is based on Pentagon figures released in February. More than 75 percent of the attacks have occurred in the past two years. Also Thursday, three Afghan women were killed in the crossfire of a battle in the east. A mortar fired during the fighting in Wardak province hit a house, killing the women inside, said Shahidullah Shahid, a spokesman for the provincial governor The battle began when Taliban fighters ambushed a NATO convoy, Shahid said. Both sides used heavy weapons, but it was not immediately clear who fired the mortar, he said. NATO forces spokesman Capt. Justin Brockhoff said reports indicate it was a joint Afghan and international patrol that came under fire. He said they were looking into reports that "civilian casualties may have been caused by the engagement." Last year was the deadliest on record for civilians in the Afghan war, with 3,021 killed, according to the United Nations. Taliban-affiliated militants were responsible for more than three-quarters of those deaths.