UPDATED 4.45PM: Auckland Police are releasing footage of two serious one-punch assaults in the CBD as they try to find the offenders.

The seemingly unrelated, unprovoked, coward punch attacks happened within minutes of each other on July 2nd.

In the first assault at around 4am on Jean Batten Place, the victim was knocked unconscious.

He suffered a fractured nose, bruises to his elbow and tailbone, and needed stitches to his head.

Just four minutes later, on Fort Street, an offender punched two people - rendering both unconscious.

Both suffered concussions - and one a displaced jaw.

A man whose teenage son was killed by a coward punch thinks New Zealand should consider a one-punch law similar to Australia's.

Across the Tasman an offender could spend life in prison for striking someone and causing their death - with lengthy minimum non-parole periods.

Here, a teenager was jailed last week for 22 months for killing a man in Invercargill with a single punch.

Anti-violence campaigner Paul Stanley is wary of mandatory sentencing, but said current sentences for these acts are absolute rubbish.

"We've got to keep these scumbags off the street for longer than 22 months. Simple. I don't care how remorseful these people are. It certainly doesn't bring the victim back and it doesn't bring the families back together."

A top police officer said introducing a one-punch law won't necessarily fix the problem.

Detective Inspector Chris Cahill said the consequences of the law are already there - the problem is, the people throwing coward punches don't think of the consequences at the time.

"These are life changing both for the people who get hit and for the offenders if they kill someone."

"It's a matter of people using some common sense and understanding how dangerous a one punch blow can be."

In some parts of Australia, that crime would carry a life sentence.