Environmental protests that have taken over parts of central London will end Thursday after 11 days, organisers said Wednesday.

"Extinction Rebellion will voluntarily end the Marble Arch and Parliament Square blockades tomorrow," said the group, adding there would be a closing ceremony at Hyde Park.

"We know we have disrupted your lives. We do not do this lightly. We only do this because this is an emergency," the group said in a statement addressed to Londoners.

More than 1,000 demonstrators blocked five high profile locations in central London, including Oxford Circus, Piccadilly Circus and Parliament Square.

Protesters set up tents, flags, sound-systems and banners, marching between their makeshift camps and parliament.

Police have arrested more than a thousand activists since they began their protests last Monday, 69 of whom have been formally charged.

Teen climate activist Greta Thunberg travelled to Britain over the weekend to support the protesters.

Addressing the demonstrations on Sunday, she declared: "the struggle has barely begun. It's only the beginning."

Extinction Rebellion is demanding that the government declare a climate and ecological emergency, act to halt biodiversity loss and reduce greenhouse gas emissions to net zero by 2025.

"Time has almost entirely run out to address the ecological crisis which is upon us, including the sixth mass species extinction and abrupt, runaway climate change," said organisers.

"Societal collapse and mass death are seen as inevitable by scientists and other credible voices, with human extinction also a possibility, if rapid action is not taken," they warned.