A manhunt is under way after three men, believed to be armed with firearms and possibly a taser, held up an armoured transit van outside an Invercargill bank.

The van was robbed shortly after 9.10am on Wednesday while it was on Spey St, near Kelvin St, outside the ANZ.

One person, thought to be a security guard, received minor injuries.

The dark green and silver vehicle used in the robbery was dumped in Leven St near the old railway station. The three men possibly left in another vehicle shortly after 9.15am and are still on the run.

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Witness Heather Raywyn Park said she was walking along Kelvin St towards the ANZ when the armed robbery unfolded.

She saw what she thought was a black with silver Subaru Legacy drive up and three men dressed in black with firearms and what appeared to be a taser, Park said.

Kavinda Herath Police interview witnesses after responding to reports of person robbing a cash transit van outside an Invercargill bank.

The men assaulted the guards, taking bags from the armoured van before making their getaway heading south on Kelvin St, she said.

The armoured transport company ACM did cash pickups and drop-offs for the bank.

A spokesperson from ACM said: "Our guards are safe, however one has sustained an injury during the incident. We are providing support to them and the impacted branch.

"We are working with authorities on the investigation and following our incident protocol, so we are unable to provide any further details that may impact the investigation at this stage."

Its "main concern is with our employees and members of the community", the spokesperson said.

They declined to comment about how much money had been taken or about if there had been similar incidents in Southland in the past.

ANZ Bank spokesman Stefan Herrick said there were around 20 staff and an unknown number of customers in the bank at the time of the van robbery.

The ANZ bank would be shut for the rest of the day, Herrick said.

Herrick later confirmed the Invercargill branch would be open at the normal time on Thursday.

John Hawkins/Stuff Police examine the getaway car used in the robbery of the armoured van on Wednesday morning and then dumped in car park on Leven St in Invercargill.

Police are still seeking any sightings of the vehicle involved on or around Esk or Dee streets shortly before 9.10am.

"We would also like to hear from anyone who saw this vehicle driving erratically either before or after the robbery."

Invercargill man Hayden Hillas said the vehicle, which belonged to his father, was stolen on Tuesday night between 7.30pm and 9pm.

They had been between 10 and 20 metres away from where the car was stolen and thought they would never see it again.

"We looked out the window and were shocked it was gone. Then we were shocked it was used in an attempted bank robbery.

"It's quite intense."

ASB, on Deveron St, has shut its doors for the day citing unforseen circumstances.

Westpac Invercargill, The Co-operative Bank, BNZ and SBS Bank have remained opened, and SBS will have a security guard at the front door for the remainder of the day.

Kavinda Herath/Stuff Police interview witnesses after responding to reports of person robbing a cash transit van outside an Invercargill bank.

While it was believed to be the first armoured van robbery in the region, other notable bank robberies include:

- In January, 2009, Mataura man Bradley Owen Sherbourne tried, unsuccessfully, to enter Westpac Bank in Invercargill. He was sentenced to 12 months' supervision

- In April, 1998, three men attempted to rob the Riverton National Bank. They unsuccessfully tried to barge through the glass control-entry doors, wielding a gold aluminium softball bat.

- On June 6 1985 Kevin David Fox, aged 32, and his wife Donna Terese Fox, aged 26, were shot dead in Gore's Main St. The pair had sent Steven Lines, who they had being holding hostage, into a bank to cash a cheque from the business account of Lines's employer.

- In March 1983, Alistair Barr and Gibson Grace stole $107,000 from the BNZ Bank in Lumsden. It was later known as the biggest bank robbery in the country.