A 42-year-old man has been charged with four counts of attempted murder following yesterday's stabbing at a Countdown in central Dunedin.

The incident happened at the Cumberland Street supermarket just before 2.30pm yesterday.

Police said three of the people injured in the attack are in a serious but stable condition in hospital. A fourth person is in a moderate condition.

They said the man was released from hospital last night and moved to Dunedin Central Police Station.

He is due to appear in the Dunedin District Court today.

Police are asking anyone who has information, including video footage of the incident, to get in touch with them via 105 and quote file number 210510/8009.

An eyewitness to the attack, who asked not to be named, said he could not believe such a thing would happen in Dunedin.

"I heard screaming. At first I just ignored it, I thought it was just kids playing around," he said.

"Then I heard these shelves falling down. Then we saw this woman, she was walking. Blood, full of blood on her face. I think she was stabbed on her forehead or something," he said.

Not knowing what to do in the moment, he sheltered in a back room for safety.

"We wanted to help this woman who was bleeding, but at the same time we were really terrified and scared. And this man, I think he ran away and he stabbed another two or three people.

"Then I saw around five or six people on the floor, I saw just blood everywhere," he said.

Police yesterday said the investigation was still in its early stages and they believe it was a random attack.

Police are working to compile witness information and collect CCTV footage.

Forensic investigators will be back at the Cumberland Street supermarket and it will remain closed today.

Police said they were continuing to make enquiries and would provide an update regarding the status of the victims and the investigation this morning.