Video report by ITV News Correspondent Juliet Bremner
Environmental protesters have blocked some of London’s busiest roads in a bid to bring the capital to a standstill.
Activists are targeting five central locations as they demand the Government declare a climate emergency.
The first human roadblock closed Waterloo Bridge to traffic in both directions on Monday morning before protesters descended onto the roads near Oxford Street and Marble Arch.
Some demonstrations have even turned violent as protesters smashed windows and vandalised doors at the headquarters of oil giant Shell in Lambeth, south-west London.
Hundreds of people gathered outside Oxford Circus Tube station around a bright pink boat, where some used makeshift devices to lock their arms together.
In Parliament Square, others unfurled banners, held up placards and waved flags as speakers took to the stage.
Some activists glued themselves to windows and smashed glass revolving doors at Shell's HQ near Waterloo, while others climbed the building to spray graffiti and hang banners.
Police said three men and two women were arrested on suspicion of criminal damage and taken to a police station in central London in connection with the incidents at the Shell offices as officers remained at the scene into the evening.
Campaign group Extinction Rebellion said it aimed to cause more than £6,000 damage so they can be tried by a jury in Crown Court.
London's protests are part of a wider campaign which will see people in at least 80 cities in more than 33 countries hold similar demonstrations on environmental issues, campaigners said.
Organisers said: "The International Rebellion begins and Extinction Rebellion will be bringing London to a standstill for up to two weeks.
"They will be blocking five of the city's busiest and most iconic locations in a non-violent, peaceful act of rebellion where they invite people to join them for several days of creative, artist-led resistance."
Protester Olivia Evershed, 23, said: "I hope that it's really going to bring awareness about the emergency crisis that we are in, and encourage the Government to act.
"They can change a few of the laws along with the Paris agreement so that we can really work towards achieving a practical target.
"We've got 12 years to act before there is irreversible damage to the environment and we start to see catastrophic changes. If we don't do anything to change this, our children will die."
Laura Jordan, 52, said: "This protest stands a good chance of working because we have a vast amount of ordinary people all saying the same thing.
"We need to change the way we do everything, the way we use fossil fuels. But this starts with the Government."
The movement has received support from actress and activist Dame Emma Thompson and former Archbishop of Canterbury Rowan Williams.
Speaking at a meditation on the eve of the protests, Dr Williams said humans had declared war on nature.
He said: "We are here tonight to declare that we do not wish to be at war. We wish to make peace with ourselves by making peace with our neighbour Earth and with our God."
Scotland Yard said it has "appropriate policing plans" for the demonstrations and officers will be used from across the force "to support the public order operation during the coming weeks".
Police advised people travelling around London in the coming days to allow extra time for their journey in the event of road closures and general disruption.