A protester glued his head to glass covering the world-famous 'Girl with a Pearl Earring' painting at a museum in The Hague this afternoon, though the artwork was not damaged, staff there said.
A second activist glued their hand to the wall next to the 1665 work by Dutch master Johannes Vermeer, and an unidentified liquid was thrown, the Mauritshuis museum said.
An unverified video on social media showed two men near the painting, both wearing T-shirts from their group.
"The police were notified and three people have been arrested. The condition of the painting was inspected by our restorer. Fortunately, the glass-covered masterwork was not damaged," the museum said.
In videos from the Dutch museum posted online, one of the men says: "How do you feel when you see something beautiful and priceless being apparently destroyed before your very eyes?"
"That is that same feeling when you see the planet being destroyed," he adds.
Dutch police said three arrests had been made at a museum, but provided no details.
The two men in the video were seen being escorted away by police in more footage.
Earlier this month, protesters threw tomato soup over Vincent van Gogh's 'Sunflowers' painting at London's National Gallery.
