A police officer shown on video body-checking a bicyclist who was riding as part of a demonstration was stripped of his badge and gun yesterday.

The incident occurred Friday evening in Times Square at the Critical Mass ride, a monthly protest of urban reliance on motor vehicles.

The video clip, posted anonymously on the Internet on Sunday, shows the officer standing in the street as bikes whiz past. The officer moves toward the cyclist, identified in a criminal complaint as Christopher Long, and violently knocks him to the ground in front of crowds of people. Another officer comes over, and the two officers wrestle with Long before handcuffing him.

Craig Radhuber said he was riding about 3 feet behind Mr. Long when he was hit.

“It was unprovoked,” Mr. Radhuber said. “It was like the cop was waiting for him and then just checked him as he got closer. I couldn’t believe it.”

The officer in the video was placed on desk duty pending the outcome of a police department investigation, the chief police spokesman, Paul Browne, said.

The video, shot by a bystander, was posted on YouTube.

Mr. Long, of Hoboken, N.J., was arrested because he was obstructing traffic in the heart of Times Square, the complaint said. He was charged with attempted assault, resisting arrest, and disorderly conduct.

The complaint said Mr. Long, 29, deliberately steered his bicycle into the officer, causing both of them to fall to the ground.

During his arrest, Mr. Long squirmed and kicked, saying to the officers, “You are pawns in the game. I’m gonna have your job,” the complaint said.

There were no other arrests in the ride.

Mr. Long’s lawyer said he hopes the Manhattan district attorney’s office will drop the charges. The district attorney’s office said it was investigating.

Meanwhile, Mr. Long’s next court date was set for September 5.

The Critical Mass bike rides started in San Francisco in 1992 and began in New York two years later. The New York rides, on the last Friday of every month, became large enough that police decided to crack down on them, leading to the arrests of more than 260 cyclists during a ride days before the GOP convention in August 2004 on charges of disorderly conduct and traffic offenses.

Dozens more cyclists have been arrested at subsequent rallies. In 2007, a federal judge ruled that the city could continue to regulate the rides despite a claim from riders arguing the rules infringe on their constitutional rights to free speech and to travel.