Sydney police have seized an AK-47 assault rifle from a house in the city's south-west.

A 46-year-old man was arrested at the home on Brennan Road at Yagoona during the raid by the Middle Eastern Organised Crime Squad yesterday afternoon.

Police say they found the rifle along with a 30-round magazine and a combat helmet.

The man has been charged with possessing a prohibited firearm and not storing a firearm safely.

The gun is to undergo ballistic examination.