One US soldier was killed and another wounded in an "apparent insider attack" in Kabul on Saturday, NATO said, in the latest such assault on international forces in Afghanistan.

"Initial reports indicate the attacker was a member of the Afghan National Defense and Security Forces," NATO's Resolute Support mission said in a statement.

The attacker was killed by "other Afghan forces", it added.

An investigation into the incident was under way, the statement said. 

The identity of the dead soldier was not immediately released.