A Kaurilands Rd resident who did not wish to be named said the incident was taking place on Meadowvale Rise, a street off Kaurilands Rd.
He said he had heard reports that an armed man was holding his partner hostage.
He said the incident had been going on for a couple of hours, and he believed police were now trying to negotiate with the man.
There were at least 10 police car, and a reasonable "police presence", he said.
Residents were waiting inside their houses.
Radio NZ has reported residents of Meadowvale Rise had been told to evacuate their homes.
"We are not allowed to leave our houses, and it started just as people were coming home from work, so people haven't been able to get home from work," the man said.
Thairanga Tanawra from T Mobile Trans Services Limited at 76 Kaurilands Road said he could see lots of police but didn't know why they were there.
Residents on the Titirangi Facebook Page were commenting on the incident.
Jude Imre wrote: "Something is going down on Kaurilands Rd, the road is blocked from Konini towards Atkinson, I think the armed defenders are also involved so it would pay to stay away. I hope all stay safe."
Lucia Williams said: "We just heard shots 10 mins ago too so went up our drive.. At least 2 dogs going nuts and police telling someone to get on the ground."
Carrie Andrea Schuster wrote: "3 rounds of gun shot ... hope all the kids managed to get home, just glad it didn't happen earlier in the day."
Donna McGee copied a post from a teacher at Glen Eden Intermediate. "I work at the intermediate they were locking it down at 6.23pm major command unit set up at back of school. They over loud speaker were stating we are armed! It's directed at a certain house. Won't way what number. A hostage situation Jesus that's why the officers were negotiating saying we want to help you. Hope she gets out ok."
Rob Taylor had just spoken to his mate in Meadowvale Rise, which was still in lockdown, he wrote. "His wife can't get in &l he can't leave his home, about 4 homes away on the same street."