4:20pm - Prime Minister Jacinda Ardern says advice from the police commissioner is they are still working on the motivation of the stabbing. Their initial assessment is it’s not terror related, but she wants to give police the time to assess it.

She says there are some early indications of what may have contributed to the incident, but says she's waiting for police to give an update later.

Ardern says she's been advised there is no one else involved.

"The advice that I've had from the commissioner of police is that they are still working through the motivation, but their early assessment, because we need to establish very early on if it's considered to be a terror-related event, there are other elements of our system that we stand up very quickly, their initial assessment is that it's not.

"But I do want to give them the time to make further assessments as to what has happened."

4:13pm - Speaking at a post-Cabinet meeting press conference on Monday afternoon, Prime Minister Jacinda Ardern said there is nothing to suggest the incident was a domestic terror attack.

She said the attack was "hugely concerning" and acknowledged the heroic actions of bystanders.

"Such an attack is hugely concerning and I do want to acknowledge the early reports of courageous acts by bystanders who have taken action in order to protect those around them," Ardern told reporters.

"Our thoughts are with all those who have been affected by this attack."

Witnesses told the NZ Herald the courageous acts of bystanders, mentioned by Ardern, consisted of members of the public tackling and pinning down the alleged stabber.

4:10pm - According to the Otago Daily Times, a witness, who was an aisle over from the stabbing, heard loud pitched screaming and mistook it for a group of teenagers. 

"I heard screaming and I thought it was just teenagers, but then I heard someone yell 'he's got a knife.'"

Another witness has told RNZ they believed the alleged offender to be high on drugs.

3:52pm - A witness has told the NZ Herald she was paying at the checkout when she heard someone yell there was somebody in the store with a knife.

She says people then began screaming and running for the exits.

3:44pm - Countdown has just released the following statement:

"We are shocked and devastated by the events in our Dunedin Central Store this afternoon," Countdown managing director Spencer Spoon says. 

"Our priority right now is our injured team members and caring for our wider team in the wake of this extremely traumatic event.  We are deeply upset that customers who tried to help our team members were also injured.

"We have been concerned about the escalating violence towards our team, and this is something we have continued to talk and raise as an issue over the last year.

"Our amazing team comes to work to serve Kiwis every day, and our customers visit our stores knowing that they will be safe. We are heartbroken that this wasn’t the case today. Our Dunedin Central store will remain closed today and tomorrow while we support our team, and we are co-operating fully with the police."

3:41pm - A witness told RNZ the man used two knife to stab people before witnesses disarmed him. Countdown has confirmed to Newshub customers who tried to help Countdown staff during the incident were also injured.

3:35pm - After initially saying five people were injured, St John has confirmed four have been taken to hospital - three with critical injuries while the fourth is in a serious condition.

3:24pm - Confirming what we know so far:

Five people, including two Countdown workers, have been rushed to hospital following a major stabbing incident at the supermarket in central Dunedin.

3:22pm - Countdown spokeswoman Kiri Hannifin, confirming two employees were injured in the incident, told Newshub the store has been closed and are providing staff with support.

3:21pm - Another witness, who was at the checkout at the time of the incident, said she heard someone say they saw a person who "had a knife", according to the Otago Daily Times.

3:19pm - Witnesses told the Otago Daily Times they have seen people covered in blood while others were running to help those injured.

Other witnesses said on social media the supermarket was evacuated and saw a man, who was bleeding, removed from the store in handcuffs. 

3:18pm - Countdown has confirmed to Newshub two of those injured in the attack were supermarket employees.

3:15pm - The Otago Daily Times reported one man seen with blood on him was apprehended just after 2:30pm. Police have confirmed one person has been arrested.

3:13pm - Countdown has confirmed to RNZ five people, two of whom were employees, were stabbed at the supermarket.

Three are in a critical condition, and two are moderate. Police said one person has been taken into custody.

Multiple police cars and ambulances hurtled into the carpark and the supermarket was evacuated.

Countdown says the store will remain closed and staff are being provided with support