VANCOUVER -- Alcohol and bravado appear to be fuelling a disturbing trend of one-punch attacks that have left three people dead, Vancouver police say.

At least 10 people this year have fallen to the ground unconscious after being hit once in the head, Vancouver police spokesman Const. Brian Montague told a news conference Thursday.

Three of the people who have died from their injuries include a 60-year-old man who was punched in front of a bar on a downtown street in August.

One-punch attacks aren't new in Vancouver, but Montague said officers have been seeing an increasing number recently, particularly in places where people are drinking.

Minor disputes are typically involved and result in serious injuries, he said.

"It's something that's disturbing to us, something that we feel is preventable," Montague said.

"In many cases these are victims who were sucker punched and not involved in any sort of consensual fight."

That was the case on Oct. 25, when a 34-year-old Richmond resident was attacked as he and his wife headed home from a comedy club late one Saturday night, Montague said.

The man was sucker punched as the pair walked past two groups of men who were arguing about a limousine in front of a bar in Vancouver's entertainment district.

"He was rendered unconscious before he hit the ground. He hit his head on the way down, suffered a brain injury as a result."

The victim, whose name was not released, was not associated with either group, Montague added.

He was rushed to hospital, where a portion of his brain tissue was removed, and he has been undergoing treatment for a month.

"The prognosis is that he will have life-altering injuries that he will be dealing with forever," Montague said.

Police are investigating and are looking to speak with anyone who may have witnessed the incident, including a woman who may have a prosthetic leg, and the drivers of the two limousines.

A 23-year-old Coquitlam man was arrested on Nov. 18 and later released on a promise to appear.

Many of the suspects in such punching cases are men who have come into Vancouver from other municipalities, sometimes looking for a fight, Montague said.

"It's other young men who have generally had a little bit too much to drink and little bit too much bravado, who aren't thinking clearly and don't realize that their actions have serious consequences."

Many of the victims have been innocent bystanders so it's difficult to say how people can protect themselves, Montague said.

Police are focusing on warning the perpetrators.

"Their lives will be forever changed because we will arrest them and they will find themselves in court," Montague said.

"Our plea is to those making the conscious decision to make their hand into a fist and take a swing. We really want them to think twice before they do that."