A St John ambulance crew were sent to the intersection of Kelvin and Earnslaw St at 9.10am, the spokesman said.
He could not confirm how the person was injured.
Invercargill resident Caitlin Barton said she saw a man lying on the footpath as she drove to work this morning.
"He was lying flat as if he had slipped on ice and had a back injury. Lots of people were crowding around him and an ambulance came flying past me ... I didn't think it was a shooting until I saw it on Facebook," Barton said.
Residents on Kelvin St posted online saying they could see the armed offenders squad from their homes, and didn't think they were allowed outside yet.
Bill Mackintosh, who lives on Kelvin St, said there were a lot of armed police in the area, including a dog van, but no one really knew what was going on.
"I went out to the supermarket and on my way home I came past a policeman with an assault rifle. He let me through to my house, though, and didn't say to stay inside," he said.
"My neighbour went down to find out what happened and thought the person might have taken off on foot, but I'm not sure if they've tracked them down yet or not."
A man at the Queens Park Golf Club nearby said he saw armed police but the scene was calm.
Police were preventing people from going down the street to the club, so he had used a side street and walked.
He wasn't worried for his safety and still planned to head out onto the green.
"Why not? No one's told us not to. No one knows what's going on."
It is not known whether anyone has been arrested.
Armed police remain in the area and a local community Facebook page said the street, near the central city, is closed.
#Breaking There's been an alleged shooting, gunman on the loose in the Kelvin and Thames Street area. Armed offenders...
Posted by What's On Invers on Friday, 29 June 2018
Anyone with information is asked to call the Southern Police District Command Centre on 03 471 5002.
More to come.
