Afghanistan ? Taliban fighters shredded a U.S. aid group’s SUV with assault rifles Wednesday, killing three Western women and their Afghan driver amid an escalating militant onslaught against humanitarian workers in Afghanistan.

The ambush of two clearly marked aid vehicles on the main road south of Kabul was the latest in a record number of attacks on aid groups this year – a surge that has workers questioning if they can safely provide services in remote and dangerous areas.

The group whose workers were slain, the New York-based International Rescue Committee, announced it was suspending its Afghan humanitarian programs indefinitely.

The aid group identified the women killed in Logar province as Nicole Dial, 30, a dual Trinidadian-American citizen; Jacqueline (Jackie) Kirk, 40, of Outrement, Quebec; and Shirley Case, 30, of Williams Lake, British Columbia.

The 25-year-old driver, Mohammad Aimal, was from Kabul and had worked for the aid group since 2002.