Climate activists attacked a famous Degas sculpture in a Washington museum Thursday, smearing its Plexiglas enclosure with paint.

The French artist's wax sculpture of 'La petite danseuse de quatorze ans' was attacked with stripes of red and black paint, the National Gallery of Art reported.

The incident was one of the first of its kind in North America.

The gallery said in a statement to AFP that the work "of inestimable value" was removed from the exhibition halls to assess possible damage.

"We categorically denounce this physical attack on one of our works of art," the gallery said, adding that the FBI was taking part in the investigation.

Activists said the assault is about global warming.

"We need our leaders to take serious action to tell the truth about what is happening to the climate," says an activist in her 50s sitting at the foot of the small statue, her hands covered in the red paint used on the glass and the base of the work of Edgar Degas, in a video published by The Washington Post.

"Today, through nonviolent rebellion, we temporarily defiled a work of art to evoke the very real children whose suffering is certain if deadly fossil fuel companies continue to mine coal, oil and gas from the soil", the group which claimed the action, which called itself Declare Emergency, wrote on Instagram.

It urged President Joe Biden to declare a state of climate emergency.

The group is unknown to the general public. It said one of its activists was detained but released by the authorities shortly afterward.

In the fall of 2022, mainly in Europe, environmental activists stepped up actions targeting works of art to seek more public awareness about global warming.

For example, they glued their hands to a painting by Goya in Madrid, threw tomato soup on Van Gogh's "Sunflowers" in London and smeared mashed potatoes on a masterpiece by Claude Monet in Potsdam, near Berlin.