An NBA Finals watch party in Manhattan descended into violent chaos on Monday night as fans brawled and police deployed pepper spray in a desperate attempt to disperse the crowds.

New York City mayor Zohran Mamdani announced a short-notice big-screen viewing at Bryant Park after the visit of president Donald Trump to Madison Square Garden forced the cancelation of a previously-planned event outside the arena itself.

5,000 free tickets were dished out to Knicks fans to watch Game 3 of the NBA Finals, but scenes turned ugly midway through the night, leading to riot police being deployed. 

It is understood the violent scenes unfolded on the streets outside the viewing party, and clips posted on social media saw huge crowds of Knicks fans brawling.

In one video, published by Freedom News TV, two men can be seen swinging punches at each other while being cheered on by a large group, before others jump in and join in with the violence. 

Others are filming the fight, and at one point a man swings around a large tree branch, before a man dressed as a superhero tries to break up the violence.

Later in the clip, a long line of NYPD officers are deployed to restore order in the crowd, and one can be seen firing pepper spray towards the crowds, shoving away particularly rowdy fans.

The unsavory scenes occurred midway through the game, and did not appear to be sparked by the Knicks losing the Game 3 showdown against the San Antonio Spurs. 

Later in the night, other fans were seen clambering over police cars as thousands of fans gathered outside the watch party.

Many of those involved in the violent scenes on the street appeared to have not been granted entry to the ticketed event on the grass inside Bryant Park. 

A separate clip showed multiple fans pulling down a street sign, as scenes turned ugly before the Knicks' defeat had even been sealed. 

The watch party near Fifth Ave and 42nd St was only announced by Mayor Mamdani a few hours before the game, in the wake of heightened security measures due to Trump's visit.

'These watch parties have become a celebration of New York City itself,' he said in a statement on Monday.

'From every borough and every neighborhood, this city has come together to cheer on the Knicks and share in a moment that belongs to all of us. 

'That's why we're adding Bryant Park as an additional watch party location, so even more fans can be part of this incredible Knicks Finals run. 

'Whether you join us in Bryant Park, Central Park or at Brooklyn Bowl, we invite New Yorkers to come together and support our team. Let's go Knicks.'