Two protesters climbed onto the stage at London's Theatre Royal during performance of William Shakespeare's "The Tempest", launching a confetti cannon, according to footage posted on social media.

Activist group Just Stop Oil said the pair held a sign that read "Over 1.5 Degrees is a Global Shipwreck" to highlight the dangers of rising temperatures.

Global average temperatures hit record highs in 2024, and over the past two years they temporarily surpassed a critical 1.5 degrees Celsius warming threshold for the first time.

The audience greeted the pair with boos and whistles along with shouts of "get them off", but by the time police arrived the pair had left.

"Two people -- a 42-year-old woman and a 60-year-old man -- were subsequently arrested on suspicion of aggravated trespass after attending a central London police station on Tuesday. They remain in custody," police said.

In a statement, Just Stop Oil named one activist as mechanical engineer Richard Weir, 60, and Hayley Walsh, a lecturer from Nottingham in central England.

"I am scared for my children," the statement quoted Walsh as saying.

"I can't sleepwalk them into a future of food shortages, life-threatening storms and wars for resources."

Weaver, 75, who achieved global fame in the 1970s and 1980s in the "Alien" franchise, plays magician Prospero in the play, which opened on December 19.