A suicide bomber killed three NATO service members on patrol in eastern Afghanistan on Sunday, officials said.
A NATO Resolute Support mission service member, an American, and two Afghan soldiers were wounded, the mission said.
The attack is being investigated.
Officials said the blast happened in the Khalazai area of Charikar, capital of Parwan province.
Wahida Shahkar, a spokeswoman for the Parwan provincial governor, said the suicide bomber targeted foreign forces who were on a routine patrol.
The Taliban, fighting to restore strict Islamic law after their 2001 ouster, claimed responsibility.