A police officer involved in a melee at Manchester Airport which saw a holidaymaker 'stamped on the head' has been stood down.
Greater Manchester Police said the officer has been removed from operational duties but has not been suspended after footage of the incident emerged on Wednesday afternoon.
Video appeared to show armed police surrounded a young man lying on the floor with his hands behind his back after being Tasered, before an officer appears to violently kick his face before stamping on his head.
A woman, believed to be a family member, watched on in horror as the man was detained, and tried to pull his head away from officers after the stamp.
Other video which has since comes to light appears to show a second man being arrested, before a female officer pushes away the woman as she stands nearby.
Greater Manchester Police said the footage was filmed after multiple officers were assaulted leaving one with a broken nose as they responded to reports of an assault in Terminal 2.
The force said it has referred itself to the police watchdog following the incident, while four men have been taken into custody on suspicion of offences including assault, assault of an emergency worker, affray and obstructing police.
Footage filmed by a witness showed a male officer stamping on one of the men's heads
A woman who appeared to be accompanying the men tried to protect her companions from the violent onslaught
Footage shows the woman was pushed away by officers, who also detained a second man who had been sat on a chair nearby.
The second man appeared to be kicked and hit as he was knocked to the ground by the same male officer.
The witness who filmed the footage, Amar Rafiq, was returning to Manchester from Qatar when he saw the incident unfold in front of him.
He told MailOnline: 'I was just gobsmacked. The police [officer] just kicked the guy in the face.
'Everyone was worried about themselves, they started panicking and rushing away, they feared they would be attacked.'
He added he did not see what happened to the men or the woman accompanying them because officers sent everyone away from the scene.
Mr Rafiq said at least ten officers were present at the time.
Other footage which has been shared online appears to show police cornering a group of people in a concourse.
In the video one officer who has his Taser out is seen pointing at a man and saying: 'You're going to get locked up.'
At this point officers move in to take hold of one person, wrestling them to the floor.
It is unclear whether this was taken before or after the video in which the man had his head kicked by an officer.
A Greater Manchester Police spokesperson said they were called to reports of an altercation between members of the public.
In a statement issued this evening, Assistant Chief Constable Wasim Chaudhry said the force understood why the video of the arrests 'created alarm'.
He said: 'We know that a film of an incident at Manchester Airport that is circulating widely shows 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.
'In advance of what is shown in the footage available, we were called to reports of an assault at Terminal 2, Manchester Airport at 8.25pm on Tuesday 23 July.
'The alleged suspect was seen on CCTV at a ticket machine in the car park and officers attended the location to arrest him.
'During our response, three officers were assaulted. One female officer suffered a broken nose and the other officers were forced to the ground and suffered injuries which required hospital treatment.
'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 force also clarified that the officer in question had not been suspended by Greater Manchester Police.
It added: 'Two men have been arrested on suspicion of assault, assault of emergency worker, affray, and obstructing police.
'Two other men have also been arrested on suspicion of affray and assault of an emergency worker.'
A second man was also seen being detained in the video - after being ordered off a chair, he appeared to be kicked and hit by the same officer
Several tasers appeared to have been activated during the incident, which unfolded at Terminal 2
In an earlier statement Greater Manchester Police had said there was a 'clear risk' that officers' firearms might be taken from them.
The spokesperson added there was a 'clear risk' officers' firearms might be taken from them.
A statement read: 'Officers were called to reports of an altercation between members of the public in Terminal 2 at Manchester Airport.
'Whilst attempting to arrest one of the suspects of the earlier altercation, three officers were subject to a violent assault, where they were punched to the ground. A female officer suffered a broken nose and all three were taken to hospital for treatment.
'As the attending officers were firearms officers, there was a clear risk during this assault of their firearms being taken from them.
'Four men were arrested at the scene for affray and assault on emergency service workers.
'We acknowledge the concerns of the conduct within the video, and our Professional Standards Directorate are assessing this.'
But the force has already faced fierce criticism online over the clip, with former Chief Prosecutor for the northwest Nazir Afzal saying: 'Obviously don't have the whole picture but I see no justification for the kick in the head, followed by a stamp and a taser on a prone, unarmed man with his hands by his side.'
Manchester Airport declined to comment.