An officer has been suspended after video footage emerged showing police kneeling on a man's neck in north London, the Metropolitan Police said in a statement on Friday.
The footage shared on Twitter on Thursday appears to show a black man being arrested in Islington by two officers. He is heard saying "get off my neck".
A second officer was removed from operational duty.
"We are aware of a video showing part of this wider incident where two officers have detained the man on the ground," the Metropolitan Police said in a statement.
"Our officers carry out their duty on a daily basis across London in often difficult circumstances. Where force is used, officers must be able to justify this as lawful, proportionate and necessary."
Metropolitan Police said it had arrested a man on "suspicion of affray" and possession of an offensive weapon.
The man is currently in police custody in London.
Deputy Met Police commissioner Sir Steve House said the footage was "extremely disturbing" and had been referred to the police watchdog.
“The man involved was arrested, taken to a police station and has now been seen by a police doctor.
“Some of the techniques used cause me great concern – they are not taught in police training," he said.
An investigation into the incident is underway.