Two climate activists stuck their hands on the frames of two paintings by Spanish master Francisco Goya in a museum in Madrid.
The protest at the Prado Museum, in which the two protesters each stuck a hand to the frames, did not damage any of the paintings but caused slight imperfections in their frames, the museum said.
Both activists were arrested after Saturday’s incident, police said.
They had scribbled “+1.5°C” on the wall between the two artworks in reference to the Paris Agreement’s goal of capping warming at 1.5 degrees Celsius above pre-industrial levels.
In a tweet, the Prado said: “We condemn the demonstration that took place in the museum.
“The works were not damaged but the frames suffered slight defects. We are working to get back to normal as soon as possible. We reject the endangerment of cultural heritage as a means of protest.
Climate activist group Extinction Rebellion uploaded a video showing the two activists each with one hand fixed to a board before museum security guards moved in.
The band said the two works in question were The Naked Maja and The Clothed Maja.
The action was a protest against rising global temperatures that “will cause an unstable climate with serious consequences for the entire planet”, the group said in a statement in Spanish.
It is the latest in a series of similar protests by climate activists targeting famous works of art in European cities.
A group splashed pea soup on a Vincent van Gogh masterpiece in Rome on Friday.
The Sower, an 1888 painting by the Dutch artist representing a peasant sowing his land under a dominant sun, was exhibited under glass and in good condition.
Four activists have been arrested, according to news reports.
Last Generation climate activists called their protest a “desperate, scientifically based cry that cannot be understood as mere vandalism.”
They warned that 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 targeted masterpieces like Leonardo da Vinci’s Mona Lisa in the Louvre in Paris or Girl with a Pearl Earring by Johannes Vermeer at the Mauritshuis in The Hague.
In October, the group Just Stop Oil threw tomato soup on Van Gogh’s sunflowers at the National Gallery in London.
All the paintings were covered with glass and were undamaged.