Gunmen in eastern Afghanistan attacked passing vehicles on a darkened highway during a midnight assault Tuesday, killing at least 13 people, authorities said.
The attack occurred in the Sayad Abad district of Wardak province's Sayad Abad district. Taliban fighters hold much of the district's territory and launch frequent attacks on security forces. However, no group immediately claimed responsibility for the assault, which comes after several recent attacks targeting buses in the country.
The gunmen opened fire around 1:00 a.m. on three separate vehicles in the attack, including a bus traveling from Kabul and heading to Ghazni province, said Attahullah Khogyani, a spokesman for the provincial governor. He said at least 13 people had died and said the gunfire wounded at least two civilians.
The bus was heading for the restive southern city of Kandahar, once a Taliban stronghold.
Mohammad Ali, the deputy governor of neighboring Ghazni province, confirmed the incident, and said the gunmen picked their victims and shot them one by one.
Both officials said the motive for the attack was still under investigation.
The killings in Wardak province underline Afghanistan's fragile security situation and come as Afghan President Ashraf Ghani, CEO Abdullah Abdullah and other top officials are in the United States meeting with U.S. officials, including President Barack Obama, about delaying plans to withdraw more U.S. troops, due to concerns about violence — at the hands of the Taliban, Al Qaeda and local militias.
Ghani has asked the US for "flexibility" as it pulls out its remaining 10,000 troops by the end of 2016, and before leaving for Washington, Ghani warned of a "difficult" spring fighting season.
Last month, gunmen in southern Afghanistan kidnapped 30 members of the Hazara ethnic community traveling on a highway in Zabul province. Security forces have been trying to secure their release ever since the attack, the latest to target Shiites in the predominantly Sunni country.
In December, the Taliban claimed credit for a spate of fatal attacks that killed more than 20 people.
Last month, masked attackers abducted 30 Shia members from the Hazara ethnic group from a bus in Zabul province. They have still not been recovered.
NATO ended its combat operation against the Taliban in December after 13 years of war, leaving Afghan forces to deal with the fighters themselves.
A smaller contingent of foreign troops, most of them American, is staying on for training and counter-terror operations.
But there have been fears that without the military muscle of the U.S.-led NATO coalition behind them, Afghan forces could struggle to quell the campaign.
In the run-up to the meeting between Ghani and Obama meeting, the prospect of the U.S. slowing its exit has become almost a foregone conclusion, with officials predicting the U.S. will likely leave many of the 9,800 American troops there now long into next year. The original plan was to cut to 5,500 by the end of 2015.
Also at stake: the future of U.S. bases in Jalalabad and in Kandahar, where the Taliban had their capital until 2001. U.S. military leaders have seemed receptive to Ghani's request that those bases stay open as long as possible.
Obama and Ghani were to discuss the pace of withdrawal on Tuesday.
Al Jazeera with wire services