Three people have been arrested after protesters from the environmental group Just Stop Oil climbed gantries over the M25, blocking traffic in both directions.
Officers were called to reports of people on the structures near junction 30 at Thurrock in Essex on Monday morning, while the motorway was also closed between junctions 6 and 7 in Surrey.
Essex Police said a man and a woman were arrested at junction 30 at 7.30am as they attempted to climb a gantry. Neither was able to climb on to the structure, they added.
They are now in custody being questioned on suspicion of road traffic offences.
A third person had locked himself onto a gantry at junction 27, which officers said took time to resolve because of "the complexities of the incident".
"We are dealing robustly and ask the public not to intervene," the force had said on Twitter.
Surrey Police said officers had decided to shut the road between junctions six and seven for a time as the force’s “protester removal team” dealt with an activist who had climbed onto the motorway gantry.
The force tweeted that it had reports there were also protesters at a number of other locations along the motorway and pledged to “get this resolved as soon as possible”.
Hertfordshire Police said five people had been arrested after protesters attempted to climb overhead gantries at various junctions.
The activist group, which is calling on the government to stop fresh investment in oil and gas projects, said it had targeted several locations around the M25.
"Just Stop Oil supporters have climbed on to motorway gantries around the M25 as part of their campaign to demand that the government halts all new oil and gas licences and consents," said a spokesman.
The group said it had warned police on Sunday night.
"Just Stop Oil contacted the Metropolitan Police and National Highways Ltd to advise them that there would major disruption on the M25, and ask them to implement a 30mph speed limit, in line with their responsibilities to keep the public safe."
The protests come as the COP27 climate conference gets under way in Egypt, with world leaders being once again urged to take serious action on climate change.
The Met Police said earlier on Monday it had begun a "significant" operation to identify and arrest climate change protesters suspected of planning “reckless and serious” motorway disruption.
Just Stop Oil staged 32 days of disruption from the end of September and throughout October, which the Met said resulted in 677 arrests with 111 people charged, and officers working a total of 9,438 additional shifts.
The climate change action group has been calling on the government to abandon plans to licence more than 100 new oil and gas projects by 2025, and to do more to help people with their skyrocketing energy bills.
Just Stop Oil vowed to continue its action, saying it will demonstrate “every day” until the group’s demand for no new oil and gas in the UK is met.
In an update on its website, the group said: “This is not a one-day event: expect us every day and anywhere. This is an act of resistance against a criminal government and their genocidal death project.
“Our supporters will be returning – today, tomorrow and the next day – and the next day after that – and every day until our demand is met: no new oil and gas in the UK.”
According to the group, since its campaign began on April 1, Just Stop Oil supporters have been arrested nearly 2,000 times, with five of their supporters currently in prison.
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