Thousands of people filled London's central Trafalgar Square on Monday in support of an environmentalist protest demanding government action on global warming and climate issues.
The protest, organized by environmentalist group Extinction Rebellion, is the first of many that are scheduled to continue over the next two weeks, according to a statement.
Thousands of people are expected to take part in their "Impossible Rebellion," said the group.
"Beginning on Monday August 23, Extinction Rebellion will take to the streets again, with plans to disrupt the City of London to target the root cause of the climate and ecological crisis -- the political economy," it added.
The Metropolitan Police have also been preparing for the event, saying on Twitter: "From Sunday, a major policing operation is under way as protests by Extinction Rebellion are set to take place in London."
At least nine people were arrested on Sunday night as climate activists tried to scale the outside of the City of London government headquarters, spraying red paint on the building.
Around 1,600 protesters were arrested in similar protests by the group in 2019 as they brought central London, including Waterloo Bridge, to a standstill for about two weeks.