It said protests would continue, with demonstrations in 33 countries around the world scheduled over the coming days.
The group expects thousands of protesters to converge on Marble Arch, Oxford Circus, Waterloo Bridge, Piccadilly Circus and Parliament Square.
All arrested protesters remain in custody as the police try to clear the disruption.
Several people were locked and glued on to a lorry parked across the bridge while others sat around eating and drinking as police and a steady stream of morning commuters looked on.
Campaigners protesting in Nottingham about the state of the environment say further action is planned over the course of the week and have pledged to "bring the entire city to a standstill".
At Oxford Circus, protesters unveiled a pink boat that says "TELL THE TRUTH" and on Waterloo Bridge demonstrators brought trees, hanging baskets and skate ramps.
Police ordered them to restrict their protest to Marble Arch after causing widespread disruption on Monday.
Protesters stand on the Shell building during the Extinction Rebellion protest.
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Environmental protesters stage a demonstration in Parliament Square London on Sunday.
"We would encourage people to check their journeys before they travel".
Environmental protesters have mobilized to take over five of London's most iconic locations, bringing streets to a standstill, with the aim of forcing the United Kingdom government to take serious action on the "global climate emergency".
Organisers said: "The worldwide rebellion begins and Extinction Rebellion will be bringing London to a standstill for up to two weeks. We've tried writing letters, we've tried voting with our feet, we've tried campaigning in all the usual institutional ways, nothing's worked, emissions keep going up year on year and so this is the last thing we can think of", Mark Ovland, another one of the protesters said. "We must act now".
"People have come up to us to thank us emphatically", she said. "But this starts with the Government".
Former archbishop of Canterbury Dr Rowan Williams has also backed the movement. "We wish to make peace with ourselves by making peace with our neighbour Earth and with our God", he said.
The XR spokesperson added: "At night Marble Arch was illuminated with XR projections reading "Act Now", "Time is running out", "Extinction Rebellion" and ominous reminders of the degrees of global warming to date and tons of Carbon dioxide emitted".