A video has been posted on Facebook which appears to show a police officer pushing a teenager off his bicycle and into a fence.

Cee La Tonga Taumoefolau posted the video on Facebook around midnight on Saturday.

It has since been viewed 18,000 times and has drawn more than 160 comments.

The teenager in the video, 13-year-old Matthew Lamar, said he and his friends had been having a music "battle" in the street in Mangere Bridge, south Auckland.

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The group of 13- and 14-year-olds attach loudspeakers to their bikes and compete to see whose music is most audible.

Matthew said he had turned off his speaker earlier because the battery was dead.

"I jumped on my bike and I was on my way home."

He said he had exchanged curse words with the officer before the incident.

"The cop got out of the car, then he threw me down off the bike. Then he picked me up and threw me against the fence and cuffed me."

Alex Eliu witnessed the incident and said Matthew had been riding on the road.

The police officer asked Matthew to get off the road and Matthew swore at him, Eliu said.

"That's when they pulled him over and said 'get off your bike'. He didn't listen, so the officer threw him off."

Matthew was handcuffed and put in the back of a police car for a short time.

"They ... told him to listen the first time and don't swear back. Then they let him go," Eliu said.

A police spokesperson said the police were looking into the incident.

"Until the full picture is established, we are unable to comment on what may have taken place," the spokesperson said.

"It is important to note that as this video appears to start part-way through communication between police and the young person, the full context and circumstances leading up to the event are yet to be determined."

Matthew said he was uninjured in the incident.