An 18-year-old man has been arrested after police raided a home in Melbourne's south-east and found what is believed to be an AK-47 assault rifle.

Police executed a search warrant at a home in Oakleigh East about 1.15pm on Tuesday and found the firearm, as well as an imitation gun.

An 18-year-old man has been arrested after police executed a search warrant at a home in Oakleigh East at about 1.15pm on August 14 and found an AK-47 firearm as well as an imitation firearm. Credit:Victoria Police

The weapons were seized, as was a quantity of what is believed to be cannabis.

The teenager was arrested at the scene and is assisting investigators with their inquiries.