Sergeant Wayne Nelson said the 43-year-old man presented at the police station watch house at 3.30am on Sunday morning with cuts, bruising and swelling to his head.

He is believed to have suffered the injuries during an incident at his Barkly Street home.

The man was taken to Portland hospital for treatment.

Sergeant Nelson said the man was unable to greatly assist police with their inquiries.

"Details are vague and we're asking for help from the public. We're still in the process of contacting neighbours to see if anyone heard or saw anything and we're calling on members of the public who may know anything to contact us," he said.

"The victim was disorientated and he's unsure what happened. Crime scene officers attended at his home. Anyone with information is requested to contact the Portland police station or Crime Stoppers on 1800 333 000," he said.

Meanwhile, a middle-aged Colac man was transported to the Alfred Hospital overnight Sunday after being assaulted.

Detective Senior Constable Chris Potter, of the Colac police crime investigation unit, said that the 56-year-old man is alleged to have been pushed to the ground about 8pm at a friend's Wilson Street home and assaulted.

"He's suffered head injuries, was taken to the Colac hospital and after assessment was transported to the Alfred Hospital in Melbourne with extensive facial injuries including likely fractures," he said.

"It appears he has been pushed to the ground by a man known to him and assaulted. We would request anyone with knowledge about the assault contact the Colac crime investigation unit or Crime Stoppers on 1800 333 000," he said.