Police arrived at a Brown Street property in Labrador at about 4.30pm yesterday after being called about a disturbance.
They began negotiations with a man who was in the residence alone and is believed to be unarmed.
An emergency lockdown was declared just before 7.30pm, with a unit block on the same street evacuated.
Some residents have remained behind and were told to stay indoors.
Drivers have also been barred from the exclusion zone.
9News understands the man police are speaking with has made threats to do harm with a gas bottle.
Multiple police negotiators are at the scene.
Firefighters have also attended.
“Some police officer came and knocked on our door (and said) ‘you have to evacuate, there is something happening’,” one resident told 9News.
A neighbour said the siege had been “pretty quiet” through the night.
