The group said protests are under way on Waterloo, Blackfriars, Lambeth and Westminster bridges.
Climate change protesters have blocked four of London’s busiest bridges on the first day of the Easter bank holiday.
Demonstrators playing bongos and waving banners reading “end fossil fuels now” and “love in action” have been pictured facing queues of traffic headed by double-decker buses.
The Metropolitan Police said they were attempting to control the disruption.
The force said: “We are aware of a number of demonstrations happening today.
“We are seeing pockets of protest which are causing delays and disruption across central Londres.
“A policing operation is in place and officers are on scene and working to manage the impact.”