A mystery man has been lying in hospital unidentified for more than a month after being hit by a Melbourne train.

Struck between Royal Park and Jewell railway stations in Brunswick, in Melbourne’s inner-north, on July 7, the man was taken to hospital with life-threatening injuries and remains in a serious but stable condition.

No phone, wallet or cards were found on the man at the time he was hit and police haven’t been able to identify him, despite extensive inquiries.

From his hospital bed, the grey-haired patient has mumbled the names “Roy and Ryan from Coburg” but it is unclear if he is referring to himself or someone he knows.

A facial composite image of the man, believed to be 65-75 years old, has been released in the hope someone will recognise him and contact Crime Stoppers.

He is described as white, about 175 centimetres tall and of medium build with a prominent mole below his left eye. He has no identifying scars and no tattoos.

-AAP