Extinction Rebellion protesters have closed London’s Tower after abseiling down the landmark.
Two activists were hanging by ropes and unfurled a huge declaring “End fossil fuels now”.
They set off red flares.
The action has bought traffic parts of London.
The bridge – a main arterial route for the city – could be closed for hours as the police try to bring down the protesters.
An Extinction Rebellion statement said:
“The action has taken place at the gateway to the City of London – the root source of fossil fuel funding in the UK – and on the eve of the April Rebellion which begins tomorrow at 10am in Hyde Park.”
The major disruption comes just a week after other protesters blocked oil facilities.