Charges laid over Dunedin stab attack

The four victims of Monday's Dunedin supermarket stabbing attack are all improving in hospital, while the man allegedly responsible has been charged with four counts of attempted murder.

New details of the horrific attack are emerging as more people present at the Dunedin Countdown supermarket share their accounts.

Two supermarket staff and a Corrections officer were among those injured.

Jenna McDowell said she was was in the toiletries aisle when she heard screaming.

"I kinda looked up and then realised that one of the staff members had been stabbed. He was just on top of her, stabbing her. She had blood around her face and I just kind of froze," Ms McDowell told TVNZ.

Ms McDowell said two shoppers distracted the knife-wielding attacker before he turned his attention to them.

Others attempted to restrain the assailant.

"They were amazing. They were heroes," she said.

"One guy had a chair against him, using all his weight just to pin him down. Yeah, cause I don't think he would have stopped if they hadn't intervened."

Police have revealed two officers at the supermarket at the time assisted at the scene.

Richard Stephenson, the clinical lead at Dunedin Hospital on Monday afternoon, said he was proud of the hospital's response.

All four victims required surgery, and while none no longer require intensive care, Mr Stephenson said all injuries were "significant" and all would have "ongoing consequences".

The accused appeared in the Dunedin District Court on Tuesday afternoon after police laid the serious charges.

A 42-year-old was granted name suppression and remanded until his next appearance on June 1.

Prime Minister Jacinda Ardern and police leaders have praised bystanders for apprehending the man, stopping further injury.

"It's nothing short of heroic," Superintendent Paul Basham said.

Mr Basham said police are still making enquiries to the man's motivation but believe it to be a random attack.

Police continue to examine the scene of the attack, taking photos and blood samples.