Shot fired in dramatic Melbourne post office robbery

Customers of a Melbourne post office were forced to the floor as gunmen opened fire during a terrifying armed robbery this afternoon.

Two men – one carrying a gun – stormed the post office in Avondale Heights, in Melbourne's northwest, about 2.30pm.

Wearing hats, sunglasses and scarves to conceal their identities, the pair demanded cash from the registers and ordered customers to get down on the ground.

One of the men fired a shot, which struck a drawer, before the two men fled the post office with an unknown sum of cash.

A woman driving an SUV in the laneway behind the post office said she almost ran over the two men and said one had "really crooked teeth".

No one was seriously injured and the two gunmen remain on the run.