Gunmen in the remote northeastern region of Afghanistan shot and killed 10 members of a medical team, police said Saturday.
The Taliban claimed responsibility for the attack that occurred Thursday.
Among the dead were six Americans, two Afghans, a Briton, and a German, said Dirk Frans, director of International Assistance Mission. He said two other Afghans on the team are alive.
The gunmen stopped the victims on a road, took their belongings and shot them one by one, said Aqa Nwor Kentoz, police chief of northern Badakhshan province. An Afghan was released because he was reciting excerpts from the Quran, Kentoz said.
The foreigners were believed to have been doctors, according to the police chief.
The mission - a non-governmental organization - has provided a number of services, including eye care and internal medicine for decades. Frans said the people were killed in what police said was a robbery.
The website said an eye-care team had been in Nuristan province "at the invitation of communities there. After having completed their medical work the team was returning to Kabul."
Hans Ronnlund, the assistant to the executive director of the mission group, denied statements by the Taliban that the medical staff was carrying Bibles. Ronnlund said the International Assistance Mission is a humanitarian development organization formed by various Christian groups, but said medical staffers do not carry Bibles.
"We cannot understand how they can say that," he said.
Badakhshan, bordered by Tajikistan to the north and Pakistan to the south, is a sparsely populated region comprised of a majority Tajik population and an Uzbek and Kyrgyz minority. Badakhshan was the only province that was not controlled by the Taliban when it ruled Afghanistan.
This tragedy negatively impacts our ability to continue serving the Afghan people," said an online statement about the organization's work in Afghanistan since 1966. "We hope it will not stop our work that benefits over a quarter of a million Afghans each year."
In Afghanistan's southern Helamnd province, international and Afghan forces killed 14 insurgents in an exchange of fire, said NATO's International Security Assistance Force (ISAF). In a separate bombing incident, two Afghans were killed and five others wounded near Heyderabad, in Helmand province.
Also Saturday, ISAF reported the deaths of two international service members in a bombing in southern Afghanistan. Their nationalities were not yet disclosed.
CNN's Samson Desta, Jill Dougherty and Matiullah Mati contributed to this report.