Ottawa police have charged two men and they have launched a review into a video posted online that shows a police officer punching a man several times.

Police say at about 11:55 p.m. Friday officers responded to a disturbance outside a bar on Clarence Street where a man was using a metal lineup pole to assault security staff.

Police said while responding, a second man punched an officer in the eye and nose, cutting him in the process. That is the man seen in the video above, police add.

Ottawa Police Chief Charles Bordeleau said he has not seen the video but he confirmed the force's professional standards section is looking into the incident.

Ottawa police Chief Charles Bordeleau says his force will review the video posted online Saturday, which shows an officer punching a man. (CBC)

The video, posted to YouTube Saturday morning, shows an altercation between police and the man in front of Tequila Jacks bar in the ByWard Market.

The video shows an officer throwing several punches near a man's head while he and another officer had the man pinned to the ground.

The video also shows a large crowd gathered around the altercation, including one man repeatedly saying, "He hit him," to the cellphone camera.

Witness thought fight was de-escalating

Kira-Lynn Ferderber said she was eating dinner across the street when a fight broke out in the line at the Tequila Jacks bar. Ferderber said she did not see what started the fight and she could not corroborate the police account of what happened at the scene

She did say she was standing near where the officer punched a man.

"It seemed like they were just trying to separate people but then it elevated to them throwing people on the ground and eventually holding a guy on the ground and punching him over and over," she said.

Ferderber said she was horrified and she did not see a reason for the officer to punch the man on the ground.

"The cops showed up and made it so much worse," she claimed.

Several charges, no complaints filed to police

Kira-Lynn Ferderber said she saw a fight break out in the line of Tequila Jacks before a police officer punched a man several times. (CBC)

The officer, who police say was punched, was treated at the scene by paramedics and the accused man who was punched, as seen on the video, also received minor injuries, police added.

That man has been charged with causing a disturbance, assaulting a peace officer, uttering threats and resisting arrest.

Another 21-year-old man, accused of using the lineup pole to assault staff, has been charged with causing a disturbance, assault with a weapon and obstructing a peace officer.

Both men were held for a show cause hearing.

No official complaints have been filed to police, Bordeleau said Saturday. He also said he does not know which police officers were involved.

"All we have is a video that appeared on Twitter and I think the prudent thing and the responsible thing for us to do is to put some context into the video and to examine exactly what did take place," Bordeleau said.

Police want any witnesses to the incident to come forward.