The siege of the Berta Cáceres started started shortly after noon when police in high-vis jackets surrounded the bright pink boat in Oxford Circus, central London, with two cordons and then steadily peeled off the Extinction Rebellion activists stuck to it.

Officers with angle grinders cut through the bars below the hull of the vessel, named after the murdered Honduran environmental activist, which protesters had chained and glued themselves to.

Five hours later, however, the tables had turned as hundreds of activist reinforcements swarmed into side roads and blocked the end of Regent Street. The police were surrounded. As officers attached the Berta Cáceres to a lorry, the crowd chanted: “We have more boats.”

By 7pm police had managed to move the boat just two streets away, only to find themselves pinned in by more rows of demonstrators singing the Beatles’ All You Need Is Love. After much obstruction the vessel was eventually driven away up Regent Street followed by jogging uniformed officers.

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Welcome to the fifth day of the Extinction Rebellion, the escalating but still methodically polite campaign of disruption that has turned several of central London’s best-known locations into a giant game of territorial to-and-fro.

Despite more than 100 arrests on Friday, taking the total to 682 by early evening, the demonstration which has blocked four major London landmarks looked set to continue beyond the weekend, with organisers preparing to extend their disruption on Monday to “picnics on the motorway.”

The activists reported an influx of supporters as the Easter holiday, balmy weather and gestures of support from school strike leader Greta Thunberg and the actor Emma Thompson injected new momentum into the weeklong climate protest.

Play Video 0:17 Police drag climate change activists near Regent Street in London - video

As on previous days, the mood was largely respectful on both sides, but video later emerged of activists being dragged roughly across the concrete near Regent Street.

Thunberg, the 16-year-old Swedish activist and founder of the school strikes for climate movement, will visit parliament on Monday and Tuesday and said she was also keen to join the campaigners on the streets.

The Metropolitan police has admitted that it is overstretched and officers said additional forces were called in from Wales and other regions to prevent Heathrow from becoming a target, but fears proved exaggerated. A group of 15 youth activists staged a two-hour peaceful protest at a road junction close to the airport.

At the biggest of the camps at Marble Arch, organisers said they had had about 300 signups in the afternoon alone, with dozens of people volunteering to work as brochure distributors. Wolfgang Wopperer-Beholz, who manned the sign-up desk, said there had been a marked increase compared with the previous day. “Earlier, the people who put their names on the list were already knowledgeable. Now we are seeing more people who don’t know so much, but are pretty enthusiastic.” He said many had mentioned the David Attenborough documentary on climate change that had aired on the BBC on Thursday night.

Induction sessions at a tent in Parliament Square were so packed that the attendees spilled outside. “It’s growing at an amazing rate. I think the Attenborough documentary lit a fire in people’s bellies,” said one of the activists, who gave only the name Archer. “They are not just the usual dirty hippies either. There are doctors, architects, and the ethnic diversity is getting wider.”

“I’ve campaigned on this for 30 years with very little effect. It’s only with Extinction Rebellion that I have a sense that we are getting somewhere,” said Bing Jones, a retired doctor from Sheffield, who was arrested and placed in a police cell in Belgravia on Thursday night. “When I was released, there was a volunteer waiting for me outside with a Mars bar and big smile. He had signed up that day, been trained, and then sat outside the police station for four hours until I came out. This is a wonderful, strange movement and new people continue to come along.”

Among the newcomers on Friday was actor Sonera Angel, who was waving a yellow banner marked with the Extinction Rebellion symbol near the police perimeter at Oxford Circus. She said she had come by train with a big group from Southend. She planned to return over the weekend and persuade more of her friends to join. “There is no excuse now it is a holiday,” she said. “Climate change is such a huge issue and governments all over the world are doing almost nothing about it.”

Facebook Twitter Pinterest Emma Thompson on the Berta Cáceres boat at Oxford Circus. Photograph: Tolga Akmen/AFP/Getty

Thompson also joined the Oxford Circus camp on Friday morning as activists read “poems to the Earth”. Later the actor gave a speech from the Berta Cáceres.

Thompson said her generation had failed young people: “We have seriously failed them and our planet is in serious trouble. We have much, much less time than we thought. I have seen the evidence for myself and I really care about my children and grandchildren enough to want to be here today to stand with the next generation.”

Organisers say the protests will continue for another week, bolstered by Thunberg, who will arrive in the UK on Sunday as part of a European tour that has included a meeting with Pope Francis and an excoriating address at the European parliament.

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Thunberg, whose strike sparked a global movement of more than a million students in less than a year, was also one of the signatories to the declaration that launched Extinction Rebellion in October. She had previously arranged to be in London after Easter to speak in parliament to party leaders and other MPs, meet fellow student activists and talk at a public event co-hosted by the Guardian.

“I would love to participate in their protests while in London if there is time and if they are still protesting,” Thunberg said. “I think it’s one of the most important and hopeful movements of our time. Civil disobedience is necessary to create attention to the ongoing climate and ecological crisis.”

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Activists and politicians say she and other young campaigners had a key role to play. “She is abso-bloody-lutely important. I thank her from my heart,” said Ronan McNern, a spokesman for the group. “It’s not Extinction Rebellion that people should watch out for. It’s the school strike for climate, it’s the youth. This is their moment.”

The climate campaigners have also been boosted by a host of prominent supporters from the science and academic communities and the entertainment world. In an open letter on Friday, the former Nasa scientist James Hansen spelled out the growing dangers of climate change and noted that he too has conducted “highly respectful acts of nonviolent civil disobedience – on occasion leading even to my arrest”.

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Linguist and activist Noam Chomsky is among those who have sent a statement of support. “It is impossible to exaggerate the awesome nature of the challenge we face: to determine, within the next few years, whether organised human society can survive in anything like its present form,” he said. “The activists of Extinction Rebellion are leading the way in confronting this immense challenge, with courage and integrity, an achievement of historic significance that must be amplified with urgency.”