"Three Resolute Support service members were killed by a suicide bomber during a combined, dismounted patrol with Afghan forces in eastern Afghanistan," it said in a statement.

A US member of the patrol and two Afghan soldiers were wounded, it said, without giving the nationality of those killed.

The attack by a lone bomber on foot happened at 6am in the city of Charikar in Parwan province some 60 kilometres north of Kabul, said provincial governor's spokesman Wahida Shahkar.

The Taliban in a statement claimed responsibility.

The US-led NATO force ended its combat mission in Afghanistan in 2014 and pulled out the bulk of its troops. A 16,000-strong residual force remains for training and counter-terrorism operations.

Last month a US soldier was killed and two others wounded in an "apparent insider attack" in southern Afghanistan, NATO said.