LONDON (AP) — Two climate protesters were arrested Wednesday for spraying orange paint on the ancient

Stonehenge

monument in southern England, police said.

The latest act by Just Stop Oil was quickly condemned by Prime Minister Rishi Sunak as a “disgraceful act of vandalism.”

The incident came just a day before

thousands are expected to gather

at the 4,500-year-old stone circle to celebrate the summer solstice — the longest day of the year in the Northern Hemisphere.

English Heritage, which manages the site, said it was “extremely upsetting” and said curators were investigating the damage. Just Stop Oil said on the social media platform X that the paint was made of cornstarch and would dissolve in the rain.

Wiltshire Police said the pair were arrested on suspicion of damaging one of the world’s most famous prehistoric monuments and a UNESCO World Heritage Site.

Stonehenge was built on the flat lands of Salisbury Plain in stages starting 5,000 years ago, with the unique stone circle erected in the late Neolithic period about 2,500 B.C. Some of the stones, the so-called bluestones, are known to have come from southwest Wales, nearly 150 miles (240 kilometers) away, but the origins of others remain a mystery.

Just Stop Oil is one of many groups around Europe that have gained attention — and received a lot of blowback — for

disrupting sporting events

, splashing paint and food on

famous works of art

and

interrupting traffic

to draw attention to global warming.

The group said it acted in response to the Labour Party's recent election manifesto. Labour has said if it wins the election on July 4, it would not issue further licenses for oil and gas exploration. Just Stop Oil backs the moratorium but said it wasn't enough.

In a statement, the group said Labour, which is leading in polls and widely expected by pundits and politicians to lead the next government, needs to go further and sign a treaty to phase out fossil fuels by 2030.

“Continuing to burn coal, oil and gas will result in the death of millions,” the group said in a statement.