Just Stop Oil protesters have thrown orange paint over a garden at the Chelsea Flower Show in London.
The Metropolitan Police said three people were arrested on suspicion of criminal damage.
A photo from the scene, shared on Twitter by the force, shows orange paint splashed across an exhibit.
In a statement, Just Stop Oil confirmed three women had thrown paint over the RBC Brewin Dolphin Garden, designed by Paul Hervey-Brookes, an award winning plantsman, after stepping over a rope barrier at 9am on Thursday.
A spokesperson said: “One of them said: ‘What use is a garden if you can’t eat?’
“Cries of dismay could be heard from the public, though this later changed to applause and cries of ‘Well done’.”
They added: “This is not a one-day event, this is an act of resistance against a criminal Government.”
The three women named by JSO were Stephanie Golder, 35, Naomi Goddard, 58, a retired landscape engineer, and Rosa Hicks, 28.
In a statement released after their arrests, Ms Goddard, from Hebden Bridge, West Yorkshire, said: “I know that by carrying out this action, I risk losing my job, my livelihood and my reputation, but it is what I have to do right now.
“We all need to do everything in our power to stop this madness continuing.
“There is a better, cleaner, safer future, but only if we fight for it.”
The Met said on Twitter: “Officers responded to an incident at #ChelseaFlowerShow this morning.
“Three people were arrested at the scene on suspicion of criminal damage in connection with a #JSO protest. Enquiries are ongoing.”
Ms Golder, from Southend, Essex, added: “I disrupted the Chelsea Flower Show to ask the visitors, exhibitors and the RHS to pick a side; to stand for good over evil, life over death, right over wrong; to stand with the young and the billions of people in the global south whose lives are being cut short by climate collapse.
“If you love gardens or growing food, you must join in civil resistance against new oil and gas.”
The incident comes after activists from Just Stop Oil – which is campaigning to end all new fossil fuel projects in the UK – interrupted the World Snooker Championship at the Crucible last month by throwing orange paint across a snooker table.
On Wednesday, six protesters were arrested on Marylebone Road, central London, the group said.
The RHS Chelsea Flower Show began on Monday and is running until Saturday.