Victoria police and a SWAT team are on the scene of an incident on the 1000-block of Southgate Street.
Police have blocked off the road, which is a few blocks from the inner harbour.
A spokesperson says officers are conducting an investigation and that there are currently no injuries that they are aware of.
Police add that some units in the area have been evacuated out of an abundance of caution
Witnesses say they heard police shouting commands earlier at someone.
The public should avoid the area.
More to come