LASHKAR GAH, Afghanistan - An air strike called in by NATO-led troops in southern Afghanistan killed 12 children and two women, Afghan officials said on Sunday, one of the worst civilian death tolls by foreign forces in months.A U.S. Marine base came under fire from insurgents in Taliban stronghold of Helmand on Saturday, the Helmand governor said in a statement, leading the base to call for help from the NATO-led International Security Assistance Force (ISAF).