A man evading police has fallen seven storeys from a car park in Southbank.

He was seriously injured in the fall of about 20 metres and was taken to hospital in a critical condition.

Security guards at the Power Street apartment building first raised the alarm after the man was spotted acting suspiciously in a car park about 3am.

When police arrived at the scene, the man tried to flee, and officers called for support before leaving the car park, Inspector Trevor Cornwill said.