Environmental protesters who have been blockading oil facilities for more than a week have been condemned by Downing Street for their "guerrilla tactics".
Activists from Just Stop Oil have been hampering access to oil terminals for days, demanding that the government stops new fossil fuel projects.
Essex Police has arrested more than 300 protesters since the disruption started on 1 April but the campaign group said some of its activists were still locked on to pipework at a terminal in Grays on Monday.
Warwickshire Police said there had been 34 arrests over the weekend linked to protests at the Kingsbury oil terminal, where protesters have tunnelled under a major access route.
A No 10 spokeswoman said: “We recognise the strength of feeling and the right to protest is a cornerstone of our democracy, but we won’t tolerate guerrilla tactics that obstruct people going about their day-to-day business.”
The spokeswoman added: “We fully support the police who are putting significant resource into their response to the demonstrations.”
The latest figures from Essex Police on Monday said 356 arrests had been made.
The force said that policing protests in Thurrock has cost Essex Police more than £1m.
Warwickshire Police said a heightened police presence was expected at Kingsbury over the coming days, with 29 arrests made over the weekend – and 180 since the April 1 protests began.
The protests, along with similar action at other sites in April, have been blamed for fuel shortages at forecourts in parts of the country.
Essex Police Assistant Chief Constable Rachel Nolan said the force was not anti-protest.
She added: “But we have been dealing with people who are trespassing into restricted areas holding flammable chemicals, posing dangers to themselves and others and it's totally unacceptable.
“Some people have already been arrested on suspicion of criminal damage.
“Their risky behaviour cannot be allowed to take place in such critical locations which could be catastrophic if there were accidental or deliberate actions causing leakage or fire.
Warwickshire Police has carried out more than 180 arrests since the protests started at Kingsbury.
Assistant Chief Constable Ben Smith said: “There remains a large police presence in the area and we can respond quickly to any concerns around suspicious activity.
“We continue to be proactive in identifying people we suspect are intent on committing criminal activity and taking appropriate action.”
In a statement, Just Stop Oil said: “Over 400 people have joined actions that have succeeded in stopping operations for up to 24 hours at a time at 11 critical oil terminals that supply fuel to hundreds of petrol stations across the Midlands and south of England.
“As many as one in three petrol stations are being reported as shut in the south of England due to the disruption caused by the actions.
“This is miserable, and our hearts go out to all those who are disrupted. No-one wants to be doing this, but it’s 2022 and right now there is a need to break the law so we are not guilty of greater crime: that of complicity with a great evil.
“We have no choice but to enter into civil resistance until the government announces an end to new oil and gas projects in the UK.”