In the most dramatic incident, a 19-year-old North Dunedin man was arrested on a drugs charge after allegedly threatening a female flatmate.
Police received a call from the woman about 11am.
A section of Dundas St, in North Dunedin, was cordoned off for about an hour from 1pm while about 15 AOS members surrounded the flat.
Senior Sergeant Craig Brown, of Dunedin, confirmed the man was believed to have weapons.
Crowds gathered to watch, but nearby residents were told by police to stay inside.
A witness said police spent about 10 minutes on a loud-hailer asking the man to answer his telephone or come out of the flat "with your hands in the air".
That was followed by 10 minutes' silence before four loud bangs were heard.
About 15 minutes later, officers led the man outside and into a police car.
Snr Sgt Brown said no shots were fired during the incident.
The officer in charge of the AOS, Inspector Dave Miller, said the four bangs heard were distraction devices.
The AOS did not find any weapons in the house and, after arresting the man, left general duties officers in charge of the scene, Insp Miller said.
Snr Sgt Brown said the man had been charged with possessing drugs utensils.
More charges were likely.
He was granted police bail and was last night in the care of mental-health authorities.
He is expected to appear in court on Friday.
Witnesses said residents had been unable to get to their flats during the standoff.
University of Otago accounting student Werner Braasch told NZPA he was going to his Forth St flat when he was stopped at a police cordon about 1.20pm.
"Quite a few" students could not get to their flats, he said.
Earlier, squad members looking for a 24-year-old Alexandra man in relation to ongoing offending in Central Otago searched two neighbouring houses in Lindsay Rd, Caversham, at 8.30am.
They did not locate the man, but arrested a 24-year-old woman on drugs charges.
About 11.15am, the squad visited a Richardson St, St Kilda, house where they located and arrested the Alexandra man.
He will appear in the Dunedin District Court today.
Insp Miller said it had been a "very busy" training day: "We did manage to get some PowerPoints in between incident one and two."
