At least 18 pro-government militiamen were killed following a Taliban ambush in Afghanistan's northern province of Balkh, officials said on Sunday.The incident occurred in village Bozboy in Sholgra district on Saturday night when Taliban militants stormed a security checkpoint, resulting in a clash that left 18 members of the Local Uprising Groups dead, an official told Xinhua news agency.The Taliban has claimed responsibility. Its spokesman Zabihullah Mujahid tweeted that a Taliban sympathizer was among the militia and he facilitated the attack.He said a Taliban fighter was killed and another wounded in the clash.Fighting has escalated in Afghanistan as the Taliban insurgency spreads from its traditional strongholds in the south and east to the once peaceful region in the north, where the Taliban have been recruiting from among the youth.The Taliban outfit and the Islamic State terror group often target civilians and religious clerics as well as local leaders for their support to the Afghan government and the US-led forces stationed in the country.