LONDON – When suffragist Mary Richardson walked into the National Gallery in London with a concealed hatchet in March 1914, she headed for the Rokeby Venus, one of Diego Velazquez’s most celebrated paintings, and slashed it repeatedly.

Now, over a century later, Velazquez’s nude appears to have been damaged again.

Just before 11am Monday, two climate activists belonging to Just Stop Oil, a British group that wants to prevent new oil and gas licensing, struck the glass that protects the painting 10 times with emergency hammers.

It was initially unclear whether they had damaged the painting.

But on Tuesday, a National Gallery spokesperson said in an e-mailed statement that “minimal damage has been sustained to the surface of the painting”.

The work – a 17th-century representation of the Roman goddess looking at her face in a mirror, originally titled The Toilet Of Venus – is undergoing conservation work, the statement added, and there was “no timeline” for when it would return to display.

Over the past year and a half, Just Stop Oil has made headlines through attention-grabbing stunts in British museums, including protests in which members glued themselves to John Constable’s The Hay Wain and threw tomato soup over Vincent van Gogh’s Sunflowers – two other artworks in the National Gallery collection.

This week’s action appears to be the first in which the group’s activists have actually damaged an artwork.

Several members have previously been found guilty of causing criminal damage in museums, but that was for damaging frames rather than the artworks they contained.

During some of those court cases, Just Stop Oil’s activists said they had discussed their plans with art experts to ensure that the potential for harm was limited.

On Tuesday, the National Gallery said it could not comment further on Monday’s incident or explain the exact nature of the damage.

A spokesperson for London’s police force said in an e-mail that the two Just Stop Oil activists had been arrested over criminal damage, because the glass protecting the painting had been vandalised.

Mr James Skeet, a spokesman for Just Stop Oil, said in an interview on Monday that because the Velazquez painting had been damaged before, the group’s actions were “not without precedent”.

He also said the group was trying to inspire the museum to take action on climate change. NYTIMES