An Afghan official says gunmen opened fire at travelers on a highway in Wardak province early on March 24, killing 13 people.
The attack occurred during a visit by President Ashraf Ghani to the United States and underscored persistent violence following the withdrawal of most U.S. and NATO troops from Afghanistan last year.
The Associated Press news agency cited Attahullah Khogyani, a spokesman for the provincial governor of the province southwest of Kabul, as saying gunmen shot at three vehicles including a bus headed south.
The AFP news agency, also citing Khogyani, suggested all 13 victims were passengers on the southbound bus.
It cited Mohammad Ali, deputy governor of neighboring Ghazni province, as saying the gunmen picked their victims and shot them one by one.
Khogyani said two other civilians were wounded in the attack at about 1 a.m. in the Sayad Abad district.
Most of the district is controlled by the Taliban, whose fighters often plant roadside bombs and attack on passing security convoys.
Ghani has asked for "flexibility" from the United States, which plans to pull out most of its remaining 9,800 troops by the end of 2016.
Ghani and President Barack Obama are expected to discuss the issue later on March 24 at the White House.