KABUL, Afghanistan (AP) — A mountain ambush by Taliban fighters killed at least 14 Afghan security force troops, authorities said Monday, as villagers elsewhere in the country alleged a NATO airstrike that the coalition said targeted militants actually killed civilians.

The fighting in Sari Pul province, as well as the disputed NATO airstrike in eastern Paktia province, show the serious challenges facing new Afghan President Ashraf Ghani Ahmadzai. Former President Hamid Karzai repeatedly clashed with NATO forces over civilian casualties from airstrikes, straining relations as public anger against the coalition grew.