Just Stop Oil has blockaded the area around Mansion House tube station during rush hour in its latest protest action.
The eco group said 31 of its activists began blocking Cannon St, Queen Victoria St and Garlick Hill from 9am.
It said some have glued themselves onto the tarmac and eight supporters have locked on to each other.
City of London Police said: “We are aware of a group of protestors blocking Cannon Street, junction with Queen Victoria Street.
“Our officers are in attendance and are working to minimise disruption. Thank you for your cooperation”.
A spokesperson for the force was unable to give more details but said they were being supported by officers from the Metropolitan Police in responding to the protest.
The group is demanding the Government stops all new oil and gas licences.
One of the protesters on Thursday, Tommy Burnett, 30, a taxi driver from Kendal, said: “I’m taking action because the status quo needs to change; we cannot continue using fossil fuels when we know it is causing increasingly severe weather and making areas of the world uninhabitable.
“I’m in civil resistance because I believe people’s health, and the health of our planet, is more important than the wealth of a few.”
It marks day 27 in the group’s month-long campaign of civil disobedience and protest.
On Wednesday, activists spray targeted several luxury car show rooms in the capital with orange paint, while demonstrators also recently threw cake on a waxwork of the King at Madame Tussauds.
Other recent protest action also includes spraying paint on the New Scotland Yard sign outside the Met Police headquarters, and targeting a Van Gough painting with soup.
