A plain-clothed New York police officer has been filmed kneeling on a man's head during a tense arrest while pointing his gun at screaming bystanders.

The incident occurred in the Brooklyn neighborhood of Prospect Heights last week when plain-clothed officers went to arrest the man for possession of a knife and a struggle broke out.

Footage filmed by a bystander and posted on social media showed the officer pressing his knee into the suspect's face as he pinned him to the sidewalk.

The officer pointed his gun at several witnesses and told the to 'get back' during the arrest.

A plain-clothed New York police officer was filmed kneeling on a man's head during a tense arrest while pointing his gun at screaming bystanders in the Brooklyn neighborhood of Prospect Heights last week

Multiple plain-clothed officers could be seen in the background arresting another man on the sidewalk.

NYPD Commissioner James O'Neill told reporters on Monday that the kneeling officer was trying to defend himself, according to the New York Daily News.

O'Neill said the tense situation was sparked when officers went to arrest the suspect but he threw wads of cash into the air to spark a frenzy among bystanders.

'This was an arrest they made, or were attempting to make, where an individual decided that as he was being arrested he was going to take whatever cash I assume he had stolen and throw that up into a crowd, creating a chaotic situation,' O'Neill said.

Police said plain-clothed officers went to arrest the man and a struggle broke out. NYPD Commissioner James O'Neill said the suspect threw wads of cash into the air to spark a frenzy and avoid arrest. A witness is pictured top right picking up the cash

Footage filmed by a bystander and posted on social media showed the officer pressing his knee into the suspect's face as he pinned him to the sidewalk

Multiple plain-clothed officers could be seen in the background arresting another man on the sidewalk who had tried to intervene in the first arrest

'If somebody does not want to be arrested, sometimes it doesn't look pretty.

'It's a hard job.'

The two men arrested in the video were identified as Carey Cruise, 29, and Edwin Barreto, 26.

Cruise petit larceny, criminal possession of stolen property, criminal possession of a weapon, obstructing government administration and disorderly conduct.

Meanwhile, Barreto was charged with assaulting a police officer, resisting arrest, obstructing government administration, menacing, disorderly conduct and harassment.