The US Open was plunged into chaos on Thursday after environmental activists disrupted play, forcing a 49-minute stoppage as the tennis showpiece became the latest high-profile sporting event to be targeted by protesters.

The semi-final clash between American teenager Coco Gauff and Karolina Muchova in the Arthur Ashe Stadium was halted in game two of the second set as four protesters wearing t-shirts with the slogan "end fossil fuels" began chanting the same message.

The protesters, from the environmental campaign group Extinction Rebellion (XR), were greeted with jeers and chants of "kick them out" by other spectators as security staff moved in.

One of the protesters glued his feet to the concrete floor of the stadium, preventing his swift removal from the arena, tournament officials said.

The drama unfolded as Muchova prepared to serve early in the second set with Gauff leading 6-4, 1-0 just after 8pm local time.

Gauff and Muchova waited patiently on the court for several minutes but eventually left the court to return to the locker rooms.

"Following the first game of the second set in the Gauff-Muchova match, play was halted due to a protest conducted by four spectators," the US Tennis Association said in a statement.

"Three of the four protesters were escorted out of the stadium without further incident. The fourth protester affixed their bare feet to the floor of the seating bowl," the statement added.

"Due to the nature of this action, NYPD and medical personnel were needed in order to safely remove this individual from the stadium."

The USTA said all four spectators had been taken into police custody.

Television footage showed Gauff and Muchova trying to stay loose in the locker rooms, consulting with coaching staff during the unprecedented delay.

Gauff and Muchova finally returned to the court at around 8.50pm local time after a stoppage in play officially timed at 49 minutes. Gauff, 19, would go on to win in straight sets 6-4, 7-5.

'Last resort' 

Extinction Rebellion said in a statement on Thursday the protest had been designed to draw attention to the "greatest emergency of our time."

"The climate and ecological crisis threatens everything on our planet, including sports," the group said in a statement.

XR activist Shayok Mukhopadhyay added that Thursday's demonstration was taken as a "last resort".

"We're not protesting the event itself; we are not protesting tennis...We are here because we have to disrupt this public event as our last resort to draw public attention to the climate emergency we are facing today," Mukhopadhyay said.

The incident is the latest in a series of protests by climate activists disrupting major sporting events around the world.

Major tennis events have been frequently targeted.

Last year a female activist disrupted the French Open men's semi-final between Marin Cilic and Casper Ruud, tying herself to the net, while in September 2022 a man ran onto the court during the Laver Cup at the O2 Arena in London and set his arm on fire.

In July this year, three people were arrested after disrupting play at Wimbledon, scattering orange confetti and jigsaw pieces over the court. The three were subsequently charged with aggravated trespass and face criminal prosecution.

In a separate incident at the Ashes cricket Test between Australia and England at Lord's in London in June, two men from the "Just Stop Oil" movement ran onto the field and scattered orange powder.

There were similar demonstrations during the recent World Snooker Championship and English Premiership rugby final.

Activists have also targeted Premier League matches and the Formula One British Grand Prix at Silverstone.