Parts of the M25 have been temporarily closed after Just Stop Oil protesters climbed overhead gantries and caused disruption on the major motorway circling London.
It comes despite the Metropolitan Police “proactively” arresting campaigners last night suspected of planning action on UK motorways.
Surrey Police said a decision was made to close sections of the M25 during the morning rush hour on Monday “for the safety of everyone” while officers removed activists.
The force said it had received reports of protesters scaling gantries at several junctions along the M25 – including between junctions 6 and 7, and junctions 8 and 9.
“We are here and dealing and will get this resolved as soon as possible,” it tweeted, adding activists had been removed from those sections of the motorway with traffic resuming.
Officers were also attempting to remove an activist between junctions 9 and 10, it added. Lanes would reopen as soon as possible, it added.
A protester also targeted junction 30 of the motorway, with Essex Police urging the public “not to intervene”.
“We are continuing to work to resolve the situation on the #M25 as quickly and safely as possible. Officers responded quickly this morning and have already made arrests,” the force tweeted.
Meanwhile, Hertfordshire Police said it was dealing with similar action on the M25, at both junction 22 (London Colney) and junction 23 (South Mimms).
“Officers intercepted a group of protestors at junction 22, and several people were arrested,” it tweeted.
“We remain at the scene, alongside specially trained Protest Removal Team officers, and a road closure has been put in place to allow them to deal with the incident as swiftly and safely as possible. Please avoid the area and seek an alternate route where possible.”
The Met had earlier said its “significant” operation had resulted in at least three people being detained, who the force had “strong reason to believe are intent on causing reckless and serious disruption to the public”.
In a statement released late on Sunday, Assistant Commissioner Matt Twist said: “Acting on intelligence, this operation is fast-moving and will continue this evening and overnight with multiple arrest inquiries under way.
“So far this evening we have made three arrests linked to this activity.
“This is an evolving situation and we suspect the intent of these individuals is disproportionate to any legitimate right to protest and clearly crosses the line into unlawful activity.
“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 suspects were arrested for allegedly conspiring to cause public nuisance, according to the Met Police.
Mr Twist warned there “remains a possibility” that other suspects are “still intent on causing unlawful disruption to the public”.
The Met has mobilised specialist teams and drawn police officers from across London to respond, he added.
“We are calling on the public to assist us,” Mr Twist said. “Remain vigilant – if you see something suspicious or witness an attempt to cause disruption call 999 immediately.
“Operations like these come at a cost. Since the start of October we have used more than 10,000 officer shifts to police Just Stop Oil protests.
“These are officers who would otherwise be dealing with issues that matter to local communities, such as knife crime, safeguarding and responding to burglaries.
“We are determined to bring to justice all of those who conspire to cause significant and unreasonable disruption to London, or cause damage to buildings, property or valuables.
“It’s what the public expects, and we’ll work closely with the Crown Prosecution Service and courts to make sure this happens.”
National Highways has secured a High Court injunction to prevent Just Stop Oil protesters disrupting England’s busiest motorway.
The court has granted a further injunction which aims to stop unlawful demonstrations on the M25, which encircles Greater London, in an attempt to end disruption to the busy road by the environmental group.
It means that anyone entering the motorway and fixing themselves to any object or structure on it, and anyone assisting in such an act, can be held in contempt of court.
They could face imprisonment, an unlimited fine, and the seizure of assets.
Just Stop Oil have this message for people who are affected
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Just Stop Oil have attracted widespread attention, and fierce criticism, in recent weeks for their stunts which have involved spraying orange paint on buildings and scaling a bridge to force the closure of the M25 Dartford Crossing.
The climate change activists 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.
The protesters have 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.