A man is in a critical condition after falling from a multi-storey building while running away from police in Melbourne.

Sorry, this video has expired Man falls from multi-storey car park

Police were called to a multi-storey car park in Power Street, Southbank, after security staff noticed a man acting suspiciously about 3:00am.

He fled when officers arrived but was found hanging from a railing on the outside of the building, approximately seven storeys above the ground.

Police tried to help him but he fell onto an awning above the ground floor before they could reach him.

Inspector Trevor Cornwill said police had not chased the man before he fell and were waiting at the bottom of the building.

"I believe he was on the outside of the building from about the seventh floor and he fell from there," Inspector Cornwill said.

"Police were going down to the bottom of the building and he fell while police were at the bottom of the building."

The man was taken to hospital in a critical condition.

Inspector Cornwill said police did not know of the identity of the man, or why he was there.

"It's pretty tragic that the male fell from such a height obviously, police were there just to speak to the male to find out why he was in the building," he said.

"Hopefully he makes a recovery and we'll be able to speak to him about why he was there."

Professional Standards Command was notified and is investigating the incident.