Three of Britain's Just Stop Oil protesters have been arrested on suspicion of planning to disrupt motorway traffic.
It came after the High Court handed down an injunction to stop activists trespassing on London's M25 ring road.
Despite this, protests took place at several junctions of the M25 on Monday morning.
London's Metropolitan Police said a motorway stunt would risk serious harm to the public.
The three people were arrested late on Sunday on suspicion of conspiracy to cause public nuisance, said Met assistant commissioner Matt Twist.
“We suspect the intent of these individuals is disproportionate to any legitimate right to protest and clearly crosses the line into unlawful activity,” he said.
“Our investigation has strong reason to suspect the Just Stop Oil group intend to disrupt major motorway road networks which would risk serious harm to the public, with reckless action to obstruct the public on a large scale.”
The injunction obtained by the National Highways agency prohibits Just Stop Oil activists from gluing themselves to the motorway.
It warns them that they could face a fine or imprisonment if they breach the court order.
Just Stop Oil activists have staged a number of eye-catching stunts in recent weeks, such as throwing soup on a painting at the National Gallery in London.
They announced a five-day pause in civil disobedience last week but said it would resume if their demands are not met.
The group's stated aim is to bring an end to any new fossil fuel exploration in the UK.