The Metropolitan Police have requested help from 200 extra officers from neighbouring forces to help deal with ongoing Extinction Rebellion protests.
The climate change protests, which have been going on since Monday, have seen at least 750 people arrested, with some taken to police stations outside the capital.
Some 28 people have been charged. Demonstrators have occupied some of the busiest spots in the capital – Oxford Circus, Waterloo Bridge and Parliament Square.
Four forces – Essex Police, Kent Police, Hampshire Constabulary and Sussex Police said they had sent officers to London under national mutual aid protocols, the BBC reported.
Scotland yard said in a statement: “One thing that is unusual about this demonstration is the willingness of those participating to be arrested and also their lack of resistance to the arrests.”
Commissioner Cressida Dick said the situation facing officers as they attempt to clear climate change protesters from blocking streets is unprecedented.
“I have never – I’ve been a police officer for 36 years – I have never known an operation, a single operation, in which over 700 people have been arrested,” she said.
She added that she was “very proud” of the work of thousands of officers over the past six days, adding that she was aware that armchair critics would feel things could have been done differently.
“We have shown that we are strong, we are determined.
“It shows we are determined and we will carry on.”
Police have been trying to confine the protests to one site in London, at Marble Arch, but the protesters have ignored the threat of arrest and continued to block other sites, including Waterloo Bridge, Oxford Circus and Parliament Square.
The Met said people were only allowed to demonstrate at Marble Arch and anyone refusing to leave other protest sites would be arrested.