Two climate activists have glued their hands to the frames of two paintings by Spanish master Francisco Goya at a museum in Madrid.
The protest at the Prado museum, in which both protesters each glued a hand to the frames, did not damage either painting but caused their frames slight blemishes, the museum said.
Both activists were detained after the incident on Saturday, police said.
They had scrawled “+1,5°C” on the wall between the two artworks in reference to the Paris Agreement target of capping warming at 1.5 degrees Celsius above pre-industrial levels.
In a tweet, the Prado said: “We condemn the protest that took place in the museum.
“The works have not been damaged but the frames have suffered slight blemishes. We are working to get back to normal as quickly as possible. We reject endangering cultural heritage as a means of protest.”
Climate activist group Extinction Rebellion posted a video online showing the two activists each with a hand fixed on a painting before the museum’s security officials move in.
The group said the two artworks in question were The Naked Maja and The Clothed Maja.
The action was a protest in the face of rising world temperatures which will “provoke an unstable climate with serious consequences for all the planet”, the group said in a statement in Spanish.
It is the latest in a number of similar protests by climate activists targeting famous artworks in European cities.
On Friday, a group splashed pea soup on a Vincent van Gogh masterpiece in Rome.
The Sower, an 1888 painting by the Dutch artist depicting a farmer sowing his land under a dominating sun, was exhibited behind glass and undamaged.
Four activists were arrested, according to news reports.
The climate activists from Last Generation called their protest “a desperate and scientifically grounded cry that cannot be understood as mere vandalism”.
They warned the protest would continue until more attention was paid to climate change.
Other actions have seen cake or mashed potatoes used in recent weeks.
They have targeted masterpieces such as the Mona Lisa by Leonardo da Vinci in the Louvre in Paris or Girl with a Pearl Earring by Johannes Vermeer at The Hague’s Mauritshuis museum.
In October, the group Just Stop Oil threw tomato soup over Van Gogh’s Sunflowers at London’s National Gallery.
All the paintings were covered by glass and were undamaged.