Key Points:

Police have launched a homicide inquiry after a man was stabbed to death in the Auckland CBD this evening.

Detective Senior Sergeant Gerry Whitley confirmed that police will begin a murder investigation after the incident, which left the 45-year-old businessman dead.

The 45-year-old man, who was carrying a briefcase, was stabbed around 530pm outside the Stamford Plaza Hotel in central Auckland.

DSS Whitley said he died at the scene after efforts by emergency workers failed.

The man reportedly staggered, covered in blood, to nearby construction workers asking for their help before a doctor who was passing by gave him medical attention.

Family members of the slain man arrived at the scene and one man tried to run past police barriers to see the body. He broke down in tears when he was stopped by Police officers.

Police are investigating whether an earlier incident involving an argument with a woman was related to the stabbing.

Dozens of bystanders watched as St John paramedic staff performed CPR on the slain man following the attack.

They stood shocked as the emergency workers' efforts failed and the man was covered with a white sheet.

Police cordons were placed on the corner of Albert Street and Mills Lane, with further cordons set up at the Mills Lane and Queen Street intersection.

The New Zealand Herald backs onto Mills Lane, and police initially stopped traffic leaving the building's carpark and took details from some staff.

Foot traffic in the area has also been halted.

One witness said he saw a man running from Queen Street up Vulcan Lane.

He said he did not know what had happened, but when he saw the police cars feared the man had been acting suspiciously and gave a statement to police.

Reports of an arrest near the scene were incorrect, police said.