SA man threatened with gun in his home

A man has been threatened by armed robbers after answering the door of his Adelaide home.

The five men demanded money after entering the Ethelton home, in the city's northwest, early on Thursday morning, police say.

The group, including a 23-year-old who was thought to be armed with a gun, fled after the victim refused to hand over any cash.

Police believe the five men and the victim are known to each other.