A suicide bomber killed three NATO service members on a foot patrol in eastern Afghanistan on Sunday, officials said, and Taliban militants claimed responsibility.
A NATO Resolute Support mission service member, an American, and two Afghan soldiers were wounded, the mission said in a statement.
"Their sacrifice will endure in both our hearts and history and further strengthen our resolve," said US Army Gen. John Nicholson, commander of Resolute Support and US Forces-Afghanistan, in the statement.
Local officials said the blast happened in the Khalazai area of Charikar, capital of Parwan province.
Wahida Shahkar, spokeswoman for the Parwan provincial governor, said the suicide bomber targeted foreign forces who were on a routine foot patrol.
Eastern Afghanistan, where US Special Forces units have regularly been deployed against militants, continues to be one of the deadliest areas for the US military since its main combat operation against the Taliban ended in 2014.
The Taliban, fighting to restore strict Islamic law after their 2001 ouster, claimed responsibility.
"We have killed eight US invaders in a tactic bombing," Zabihullah Mujahid, the Taliban spokesman, said in statement.
"The invaders had to bring three helicopter ambulances to protect their forces," he said.