"Last Generation" published footage of the "Oil" campaign on their Twitter account: They show how one of the activists pours black liquid from a hot-water bottle onto the painting, while a second one sticks his hand to the painting. Before the first activist is overwhelmed by a museum guard and dragged out of the hall, he calls out: "Stop the destruction of fossils. We're racing into a climate hell."

Admission to the museum was free on Tuesday as part of a special promotion sponsored by Austrian oil company OMV. The two activists accused the group and other companies of wanting to "wash a clean slate" with such financial support - just like "the tobacco industry back then".

The climate group describes itself as "the last generation that can still stop the absolute climate collapse". You and other climate activists have been causing a stir for weeks with spectacular actions against works of art. Victims of their actions included a painting by Goya in Madrid, Warhol's "Campbell's Soup" in Australia, Van Gogh's "Sunflowers" in London and Monet's "Grainstacks" in the Potsdam Museum Barberini.

Dozens of the world's most important museums had sharply condemned the attacks last week. Those responsible underestimated "the sensitivity of these irreplaceable objects that must be preserved as part of our world heritage," wrote the directors of more than 90 museums such as the Prado in Madrid, the Louvre in Paris and the Uffizi Gallery in Florence.