Light planes crash after mid-air collision as emergency services rush to the scene at Port Phillip Bay

Emergency services are desperately searching for survivors of a plane that ditched into the sea off Victoria.

The plane entered the water near Mount Martha, south of Melbourne, about 1.45pm on Sunday.

The Australian Maritime Safety Authority has reported the wreckage has been located but it is not yet known if there are survivors. 

Radio station 3AW has reported a former military aircraft, an S-211 Viper jet, ditched into the water, with a pilot and passenger believed to be on board.

Crash debris has been spotted on the water where the emergency service workers are searching.

S-211s are Italian-made fighter planes primarily used for Royal Australian Air Force training.

It is believed two aircraft collided about 12km west of Mornington.

While one of the aircraft crashed into Port Phillip bay the other was able to land at Essendon airfield.

Police and emergency services have gathered along the cliffs near Hearn Rd.

At least four helicopters, including police and air ambulance, are searching the water near the crash site.

A number of water vessels, including coast guard and jet skis, are also joining the search.

More to come