Three civilian men, including a US engineer, were shot dead by armed men while driving on the road from Kabul to Bamyan on Monday afternoon, local officials said.
The two other men were Afghan nationals, one an engineer and one a driver.
The shooting happened in central Parwan province's Seyagerd district while they were on the Kabul-Bamyan highway, a spokesman for the 202nd Shamshad Military Corps Ebadullah said.
"The two Afghans, the driver and one of the [American] man's colleague's, were shot dead by gunmen," Ebadullah said.
"The gunmen were in a car and they escaped from the area. A resident of Parwan was also injured the attack," he added.
Some reports said that the American national was an electrical engineer who had worked in Afghanistan for about 30 years.
The Taliban claimed responsibility for the killings via their spokesman.