A group of activists on Friday splashed pea soup onto a Vincent van Gogh masterpiece in Rome, in a protest they warned will continue until more attention was paid to climate change.
"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".
"Non-violent direct actions will continue until citizens get answers from their government on the demands to stop gas and coal and to invest in at least 20 GW of renewables," they said in a statement.
Video images taken from inside a museum gallery crowded with visitors show two young women throwing a liquid substance onto the painting.
They and a third woman are then seen gluing their hands to the wall as shouting erupts in the room.
"For shame!" someone in the crowd can be heard shouting.
- 'Ignoble act' -
Climate activists have carried out a series of attacks -- using soup, cake or mashed potatoes -- in Europe 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 of those paintings were covered by glass and were undamaged.
"Everything that we would have the right to see in our present and our future is being obscured by a real and imminent catastrophe, just as this pea puree has covered the work in the fields..." Last Generation said in its statement Friday.
Italy's Culture Minister Gennaro Sangiuliano condemned the protest, calling it an "ignoble act that must be strongly condemned".
"Culture, which is the basis of our identity, should be defended and protected, certainly not used as a megaphone for other forms of protest," Sangiuliano said in a statement.
"The Sower" is on show at Rome's Palazzo Bonaparte, part of an exhibition of 50 paintings by Dutch master Van Gogh on loan from the Kroller Muller Museum in Otterlo in the Netherlands.
The exhibit organisers, Arthemisia, did not respond to a request for more information on the attack.