U.S. military

The commanders said the decision came about because of a fragile security situation highlighted by the Taliban's capture of the northern city of Kunduz this week as well as recent militant inroads in the south.

Keeping any substantial number of troops in Afghanistan beyond next year would mark a sharp departure from President Barack Obama's existing plan, which would leave only an embassy-based security cooperation presence of about 1,000 military personnel by the end of next year. 

Brig. Gen. Wilson Shoffner says in a statement issued Tuesday that "based on information we received today, we feel it is prudent to investigate the airstrike our forces conducted in Kandahar" on Sunday.

An Afghan official, who spoke on condition of anonymity because he was not authorized to release information, said Monday that a NATO airstrike the night before in neighboring Helmand province killed the 11 during an operation to arrest drug smugglers.

A spokesman for Central Command, Air Force Col. Patrick Ryder, told reporters at the Pentagon on Friday that the hacker, Junaid Hussain, also was responsible for the recent release of personally identifying information on about 1,300 U.S. military and government employees and sought to inspire violence against U.S. service members.

Ryder called Hussain a key IS member. He said he was killed Monday in an airstrike in Raqqa, the city the Islamic State group considers its capital.