Extinction Rebellion climate protesters forced the closure of the Tower Bridge crossing over the River Thames in London.
Large numbers of police officers were at the bridge for the protest, and helicopters hovered overhead as efforts were made to reopen the route on Monday.
Demonstrators stopped a van and caravan on the Victorian bridge, and police made arrests.
Protesters in aprons emblazoned with the phrase "Tell The Truth" and teapots with "Deniabilitea" written on them were seen at the South Bank end of the bridge.
Extinction Rebellion has been staging two weeks of protests across sites that included Buckingham Palace and Trafalgar Square.
Tower Bridge is a key route crossing the Thames, linking the Shad Thames area to the Tower Castle and City of London.
The bridge was shut to traffic as protests continued.
“In the last couple of moments, protesters have blocked Tower Bridge,” London’s Metropolitan police tweeted.
“Activists are using a van and a caravan to obstruct the road. Officers were on scene almost immediately.
“We are working with @CityPolice to get traffic moving again.
“Activists are also lying on the junction north of Tower Bridge, this is causing further disruption. We will provide further updates soon.”
Extinction Rebellion began its Impossible Rebellion protests a week ago.
It wants the British government to end its investments in fossil fuels, which cause climate change.
Campaigners also demonstrated outside the Department for Business, Energy and Industrial Strategy last week, and hundreds of people marched through St James’s Park towards Trafalgar Square, where a band blocked the road.
The protests come before the UK hosts the Cop26 environmental summit in November and after a series of UN reports warning of the increasing danger of climate change.