Three people have been put on remand for a month over an Extinction Rebellion protest in which activists climbed on top of a train at Canary Wharf station in east London.

Cathy Eastburn, 51, from south London, Mark Ovland, 35, from Somerton in Somerset, and Luke Watson, 29, from Manuden in Essex, were charged with obstructing trains or carriages on the railway by an unlawful act, contrary to section 36 of the Malicious Damage Act 1861, over the protest on Wednesday that halted Docklands Light Railway (DLR) services.

On Wednesday the three pleaded not guilty at Highbury Corner magistrates court. The district judge Julia Newton denied them bail and remanded them in custody to appear at Blackfriars crown court on 16 May. The maximum prison sentence under the charge is two years.

The move came as organisers promised to create further disruption with swarming roadblocks on the streets of central London as the protest entered its fourth day, anticipating the arrival of reinforcements from Extinction Rebellion groups elsewhere in the country. On Thursday morning activists reported that they were staging roadblocks on Vauxhall Bridge. They hope more Londoners, freed from the constraints of work by the long Easter weekend, will also join in.

Q&A What is Extinction Rebellion? Show Extinction Rebellion is a protest group that uses non-violent civil disobedience to campaign on environmental issues. Launched in October 2018, with an assembly at Parliament Square to announce a 'declaration of rebellion' against the UK Government, the group has staged regular demonstrations against current environmental policies. More than 1,000 activists were arrested in April 2019 after protesters occupied four sites across London, as well as blocking roads, disrupting a railway line and conducting a protest at Heathrow. Other demonstrations have included a semi-naked protest inside the House of Commons and blockading streets in London, Cardiff, Leeds, Bristol and Glasgow. The group says climate breakdown threatens all life on Earth, and so it is rebelling against politicians who “have failed us”, to provoke radical change that will stave off a climate emergency. The movement has become global with groups set up in countries include the US, Spain, Australia, South Africa and India. Martin Belam Photograph: Anadolu Agency/Anadolu

On Thursday afternoon police continued to enforce their section 14 order in Oxford Circus. Under the order, protesters have been told they can continue their demonstration at Marble Arch.

The Guardian watched as police carried away one protester after another, while crowds chanted “tell the truth” and “we love you” as each person was taken away.

No music played from the stage in the early afternoon, but speakers addressed the crowd through a megaphone and drummers played lively rhythms to accompany every cheer.

Emmy Stocking, 35, a landscape gardener from Bury St Edmunds in Suffolk, was handing out free food from a tent. “So far it’s just been lovely vibes,” she said. “Police have been arresting people but the atmosphere is awesome.”

It was quiet at the Marble Arch site on Thursday, where activists have been camping all week. A woman played acoustic guitar and sang folk songs from the solar-powered stage while passersby visited information stands or got clothes printed with Extinction Rebellion logos.

On Wednesday evening, protesters had resisted renewed attempts by police to remove them from Waterloo Bridge, Oxford Circus and Parliament Square.

The Guardian witnessed at least a dozen arrests on Waterloo Bridge on Wednesday evening, while activists reported between 30 and 50 arrests in Parliament Square. The Metropolitan police had made 428 arrests as of 9.30am on Thursday, but a Met spokesperson said the force was only updating arrest numbers twice a day.

Protesters in Parliament Square on Wednesday. Photograph: Ollie Millington/Getty Images

The protests have continued despite police imposing conditions at three of the four sites where protesters have blocked traffic since Monday. Parliament Square, which was partially seized by police after they appeared in large numbers early on Wednesday evening, was dramatically retaken later the same night by protesters who arrived with a samba band and re-established roadblocks.

Bing Jones, 66, a retired NHS doctor from Sheffield, said: “It’s remarkable, because there was an absolute troop of police marching in military style in a great long line. But lots of us lay down on each roadblock and managed to hold three of the five exit points from the square. It was quite exciting because they came in such numbers that it looked as if they were going to swamp us.

“They took a certain number [of activists], then looked at the number of us and left. I think that’s the story of Extinction Rebellion: the police come, they have a policy to arrest, they arrest and arrest and arrest, then they just can’t take any more; they look at the quantity of people waiting to be arrested and then they just give up.

“It was then just so wonderful because the police suddenly evaporated, but there were still lots of us and we had a samba band and lots of supporting people who arrived. As the night wore on there were so few of them that we were able to retake the two junctions … so we basically control Parliament Square again.”

On Waterloo Bridge police arrived in large numbers at about 7.30pm, walking through the crowd and serving section 14 notices on people there. Those who refused to leave were picked up and carried away to waiting police vans.

Police have come under heavy criticism for apparently targeting legal observers – volunteers who collect evidence on protesters’ behalf during interactions with officers – as they worked on the bridge. The Guardian witnessed officers pointing out the observers, who wear orange tabards, before moving in to serve them with notice to leave.

One observer, Stu Daniel, from Devon, who was arrested on Tuesday, said he had never seen police target legal observers before. “We are impartial in our note-taking,” he said. “We aim to facilitate a peaceful arrest process for activists choosing to take that step. We are a strong symbol and a deterrent for the very rare but occasional occurrence of heavy-handed police behaviour and, equally, can provide a reminder were there to be any slips from [Extinction Rebellion’s] non-violent protocol in protester behaviour.”

Daniel said he was clearly note-taking when police moved in to arrest him. “Previously I’ve only ever had positive interactions with the police,” he said. “I was shocked that I was targeted. Since then the police have targeted and arrested many of our legal observers. Why? My best guess is that they think the protesters will feel more vulnerable in our absence. It’s a psychological move.”