Continuing their search for a suspect in a violent daytime attack on a city bus driver, police in Winnipeg have released video footage of the incident.

The video footage of the Sept. 14 attack – which was released Tuesday -- shows the suspect boarding a city bus and asking for a transfer. But when suspect’s request is refused because he has not paid a fare, the unidentified male starts violently attacking the driver.

The suspect proceeds to strike the driver for nearly three minutes. Police said the attacker stopped after two men boarded the bus to intervene.

Winnipeg police Const. Eric Hofley told CTV Winnipeg that the video was released in order to send a strong message.

"We need to be clear that this type of behaviour is unacceptable," he said.

The Amalgamated Transit Union said that there have been 25 assaults on bus drivers this year.

And despite cameras being installed on Winnipeg's buses in 2009, the union says they've not seen a drop in the number of assaults.

"We have had an increase of assaults over the last couple of years, compared to what we had 20 years ago, 25 years ago," union president Jim Girden said.

Photos of the suspect were initially released after the attack, but the union believes the extra video footage will help the investigation.

"The message needs to be given (that) we will try to find you and these videos will hopefully help us do that," Girden said.

Bus passenger Lenny McKay agrees.

"If they're trying to find somebody… I think the pictures and video of what they look like should be released to the public," he said.

The bus driver suffered minor injuries in the attack and has since recovered.

Anyone with information about the case is asked to call Winnipeg police at 204-986-6668 or Crime Stoppers at 204-786-8477.

With a report by CTV Winnipeg's Alesia Fieldberg