A police officer kicked and stamped on a man’s head as he was lying face down on the ground at Manchester Airport.
Footage, widely shared on social media, showed the officer, with a Taser in his hand, kicking and then stamping on the head of a man.
A second man was also struck by the officer.
The video is being “assessed” by professional standards, the force has said.
In response to the video, Greater Manchester Police said firearms officers had been responding to reports of an altercation between members of the public.
They said a female officer involved suffered a broken nose and that all three responding officers were taken to hospital.
The force said “there was a clear risk during this assault of their firearms being taken from them,” and said they “acknowledge the concerns of the conduct within the video”.
Four men were arrested for affray and assault on emergency service workers, police said.
Manchester Airport said: “We are aware of an incident involving Greater Manchester Police officers that took place yesterday and, as a result, the force is investigating the matter.
“We will support the investigation in any way possible.”
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