Incident is being investigated by the NYPD's Internal Affairs Bureau

He was being cuffed by 3 officers in Manhattan when man launched in

Footage has emerged of a plain-clothed New York police officer punching a teenage boy repeatedly in the back as he was being handcuffed by four other police on Monday.

Witnesses claim the suspect was just 12. The NYPD says he is actually 16 years old and has a history of arrests.

The case has been referred to the Internal Affairs Bureau for investigation and the NYPD is saying very little about the details of the arrest.

Scene caused outrage on the streets of the Lower East Side of Manhattan on Monday afternoon. The NYPD has come under increasing scrutiny for its use of force in the wake of the Eric Garner case.

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'Attack': Witnesses screamed filming this moment a man believed to be a cop punched a boy being arrested

'Punch': Footage appears to show the man punching the boy as officers move to let him into the circle

The officer who struck the blows (left) has not been identified. The case is being reviewed by the Internal Affairs Bureau

Garner, a black man, died after a white officer applied an alleged chokehold while arresting him for selling un-taxed cigarettes this summer. When a grand jury opted not to indict the officer last month, thousands took to the streets of New York in protest.

In the video taken on Monday, the teen appears to be resisting officers who are attempting to handcuff him.

Suddenly, a plain-clothes cop runs up from behind and punches the teen several times in the side.

Witnesses filming the attack on Monday at 4pm screamed at the man to stop.

'Hey! Hey! Hey! Stop it! Get off of him!' one woman yells at the officers.

One woman shouts that the suspect is just 12 years old. She identifies herself as a lawyer and says: 'I can’t believe he just did that after everything that’s happened.'

'Get a different profession, this is not a war. Go to war, the woman jeers.'

Screams: Witnesses screamed at the man to stop as the boy, believed to be 12, lost his footing

Actress Sarah Doneghy, who caught the incident on her phone camera, said on YouTube: 'This happened today on my way to the post office.

'The kids were 12. They had supposedly pushed one of their classmates down.

'However when the victim was asked, he said those weren't the guys.'

'They were still taken away,' Doneghy added. '12. Years. Old.'

The NYPD says the suspect is actually 16. Officers say the teen has a history of arrests. He and two others were arrested for assaulting someone who walked with a cane.

'The incident is under review. And the allegations have been referred to our internal affairs bureau,' a spokesman told MailOnline.