Protesters have thrown red soup at the Mona Lisa painting in the Louvre in Paris.
Footage shows two women crossing a security boundary to get closer to the painting, with both throwing soup towards the Leonardo da Vinci artwork.
Both are wearing a shirt with Riposte Alimentaire - which translates as food response - written on the front, referring to a climate activist group.
The incident came as French farmers protest for days against low wages, rising costs and regulations.
"What's the most important thing?" the women shouted. "Art, or right to healthy and sustainable food?"
"Our farming system is sick, our farmers are dying at work," they added.
Museum staff then rushed to the painting with black screens in a bid to block the public's view and asked visitors to evacuate the room immediately.
Two people were arrested following the incident, Paris police said.
A glass window protects the Mona Lisa, meaning the soup would not have covered the painting itself.
Riposte Alimentaire claims two people - aged 24 and 63 - involved with their "new campaign" were behind the incident to "demand the establishment of sustainable food social security".
Angry French farmers have been using their tractors for days to set up blockades and slow traffic across the country as they protest for better pay for their produce.
Also seeking less red tape and protection against cheap imports, the farmers said a series of measures announced by the government on Friday does not fully address their demands.
As a result, some farmers threaten to converge on Paris, starting on Monday, to block the main roads leading to the capital.
The world's most famous artwork has been targeted before.
In May 2022, cake was smeared on the covering, with bystanders claiming a "man dressed as an old lady" jumped out of a wheelchair before trying to smash the protective glass.
The gallery explained the culprit had managed to get close to the portrait by "simulating a disability", allowing them to take advantage of a policy designed to help people with mobility problems see the major works in its collection clearly.
One man was seen saying "think of the planet" after the incident.
Activists from Just Stop Oil have targeted artwork elsewhere recently, with other attempts including throwing soup at Vincent Van Gogh's Sunflowers at London's National Gallery in October 2022.
In the following month, campaigners glued themselves to Goya paintings in Madrid's Prado museum.