The activist group Letzter Generation (Last Generation) on Sunday posted a video showing two of its activists throwing a viscous liquid on a Monet painting at a gallery in Potsdam near Berlin.
Two young people each threw what they described as mashed potatoes on the "Meules" (Haystacks) painting by Claude Monet, before crouching in front of it with one of them delivering a short statement.
They alluded to the attention previous such protests in recent weeks have generated.
"People are starving, people are freezing, people are dying. We are in a climate catastrophe. And the only thing you're afraid of is tomato soup or mashed potatoes on a painting," the young woman said.
"Do you know what I'm afraid of? That science say that we will not be able to feed our families in 2050. Does it take mashed potatoes on a painting to make you listen? This painting will be worth nothing when we are fighting over food. When is the point that you will finally listen and not just carry on as before?," she continued.
Two other protesters glued themselves to the floor as part of the demonstration.
A police spokesman told the German dpa news agency that two of the protesters were arrested and were being investigated for potential trespassing and damage of property.
Was the painting damaged?
A spokeswoman for the Museum Barberini in Potsdam, Carolin Stranz, told dpa that it was not yet clear whether the painting had sustained permanent damage.
Past such protests, including one targeting one of van Gogh's Sunflowers works in London, had sought to target paintings displayed behind some form of protective covering. In that case, the painting sustained only light damages.
Stranz said the Monet in question was protected by a glass frame.
The painting, part of impressionist Claude Monet's series of Haystacks, hangs in the permanent exhibition of the Museum Barberini. It is part of a collection at the museum founded by multi-billionaire Hasso Plattner, a co-founder of the SAP business software behemoth.
Deliberate tactic to generate discussion?
As Sunday's protesters alluded to, demonstrations of this nature have prompted unusual media attention by the standards of many climate protests, courting both support and criticism.
Last Generation have also been staging protests targeting roads and highways in Germany, sitting on or gluing themselves to the asphalt. Recently, several of its activists have also attached themselves to various artworks.
Leading members of the group also famously went on hunger strike demanding an audience with would-be Chancellor Olaf Scholz during the German election campaign, which they received in November of last year.
msh/aw (dpa, epd)