A video showing a British police officer kick and stamp on a man's head during an arrest at Manchester airport in northern England sparked a protest outside a police station late on Wednesday night.
Police said they had referred the actions to an independent complaints watchdog after the video, filmed by an onlooker, was posted on social media platforms and attracted immediate criticism.
It showed a chaotic scene in an airport parking lot in which several officers armed with tasers restrained two suspects. One man was kicked and stamped upon as he lay face down on the floor. The second man also appeared to be struck in the head by an officer.
A Greater Manchester Police (GMP) statement said the video showed "an event that is truly shocking, and that people are rightly extremely concerned about. The use of such force in an arrest is an unusual occurrence and one that we understand creates alarm."
It said police had been responding to reports of an assault occuring in Terminal 2 at Manchester Airport, and that three officers were themselves assaulted during their response. The officers required hospital treatment, including one female officer who had a broken nose.
The police further noted that during the incident, since the police officers were carrying firearms, there was "a clear risk during this assault of their firearms being taken from them."
'We acknowledge the concerns about the conduct in the video'
"One male officer has been removed from operational duties and we are making a voluntary referral of our policing response to the Independent Office of Police Conduct," the statement added.
The two men were arrested on suspicion of assault, assault of an emergency worker, affray, and obstructing police.
"We acknowledge the concerns about the conduct in the video, and our Professional Standards Directorate is assessing this," Greater Manchester Police noted in their report.
The incident sparked a protest outside a police station in a nearby town. One videos posted online showed the crowd of at least 100 people chanting "Shame on you GMP".
Police, who have not confirmed any details about the identity of those arrested at the airport, said the protest concluded safely and without incident.
"We have spent the evening listening to community feedback and will continue to engage with communities and elected members to maintain strong partnership links and understand local views," they said in a subsequent statement.