A witness to an "unprovoked and violent" armed robbery of a central Auckland dairy has told of seeing a man covered in blood and holding a knife.

Kaustab Roy, of Grey Lynn Fine Wine and Spirits, said he was serving a customer around 7.15pm last night when a man came in and asked him to call the police.

"I didn't understand why he was like that because I was with a customer, so I finished the trade and the guy came back.

"He told me to call police because someone had stabbed the people next door," he said

"I took out my mobile phone and gave it to him so he could explain what he had seen to the cops."

The Hylite Dairy in Grey Lynn this morning. Two people who were stabbed are in hospital recovering. Photo / Peter Meecham

Roy said he left the liquor store and saw the offender walk across the street.

"He walked away in front of me and he was around 22 years old. In his right hand was a knife and it was full of blood," he said.

Roy went to the dairy and found two people he knew well with serious injuries.

"I know them from working beside them.

"The guy was badly injured on his stomach and the back of his shoulder. His mother was also injured on the forehead and she was begging for help and screaming for an ambulance," he said.

"There was another guy who was living upstairs to their shop so he was helping to stop the blood and calling the ambulance at the same time."

A mother and her adult son are now recovering from surgery after being stabbed during the robbery at the Hylite Dairy on Great North Rd, Grey Lynn.

Auckland City District Commander Superintendent Karyn Malthus said detectives were talking to three people about the aggravated robbery.

"This appears to be an unprovoked and violent attack and police are determined to hold the offenders to account," Malthus said.

Auckland City Detective Sergeant Martin Friend said two men went into the store, one carrying a knife. After a "physical altercation" behind the counter they ran towards Tuarangi Rd.

"One person inside the store, a male, received stab wounds and is in a critical condition in hospital," Friend said.

"A second person received a wound to their stomach and head, and is in a less 
serious condition."

Friend said it wasn't clear whether anything was stolen from the shop.

Police cordoned off the dairy last night and investigators worked until 4am.

Roy said the whole experience was "definitely a scary thing" but he hoped security systems inside the liquor store would help keep him safe.

"Working in a liquor store is obviously very dangerous but I had never thought it could be like that," he said.