Photo: vicpolicenews

Police have been told the 23-year-old man had left a King Street venue when he became involved in a verbal argument with an unknown man in Flinders Lane about 6.10am.

The man has grabbed the Altona Meadows man, placed him in a headlock and punched him to the face.

The man was knocked unconscious and fell backwards onto the concrete.

The unknown man ran away as witnesses assisted the injured man with first aid.

The victim was taken to hospital at the time, where he was treated for a serious head injury.

Police have released a new image of a man who they believe may be able to assist with their investigation.

The unknown man is described as being about 185cm to 190cm tall, with a solid build, short, light-coloured hair.

He was wearing a plain black t-shirt, dark-coloured jeans and black shoes.

Police are urging anyone with information to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.