Five people have been killed in a shooting at an apartment complex south of Seattle in the US state of Washington.

The suspect, who was shot by officers responding to the scene, was among the dead.

Police spokeswoman Cathy Schrock said officers responded to an emergency call of shots being fired in Federal Way yesterday at 9.30pm (local time).

Federal Way is about 30km south of Seattle.

Arriving police spotted two men on the ground in a car park, one of whom reached for a gun as the officers moved in to assist.

Ms Schrock said officers then opened fire. The man was killed but it was not immediately clear if it was from police gunfire.

The other man on the ground and a third man in the car park were found to be dead.

In a search of the complex, police found yet another man dead in one apartment and a slain woman in another.

There was no immediate word on what set off the gunfire.

The names of the dead were not immediately available.