Climate change activists climbed on a train and glued themselves to the carriage in the third day of protests aiming to “shut down London”.
Extinction Rebellion protesters have been blocking traffic at Marble Arch, Waterloo Bridge, Parliament Square and Oxford Circus since Monday.
Wednesday’s action – affecting a Docklands Light Railway (DLR) train at Canary Wharf – caused minor delays.
More than 300 people have been arrested this week over the protests.
A campaigner who glued himself to the train’s window was removed about an hour after the start of the DLR protest, at about 10:50 BST.
A man and a woman who unfurled a banner and glued themselves to the top of the train’s carriage were also later removed and carried off by officers.
BTP said three people had been arrested for obstructing the railway.
Extinction Rebellion targeted the DLR after members changed their minds about disrupting the Tube network.
Earlier, BTP ordered Transport for London (TfL) to switch off wi-fi at Tube stations to deter protests.
Supt Matt Allingham said extra officers would be on duty throughout the day, adding: “We will not tolerate any activity which disrupts the millions of passengers who rely on using the rail network in London.”
Campaigners at Waterloo Bridge and Oxford Circus have been ordered to restrict their protests to Marble Arch.
The Met said protesters were being removed from both areas and that those who did not comply would be arrested.
The BBC’s Dominic Casciani said about a dozen people were carried to police vans at Oxford Circus after failing to comply with police.
Most of the people arrested so far have been held in connection with public order offences.
The Met Police said “contingency plans are in place should custody suites become full”.
Extinction Rebellion earlier said “thousands” more people were willing to be arrested as part of the non-violent disruption.
It had been planning to target London Underground to “highlight the emergency of ecological collapse” and persuade ministers to meet group members.
On Wednesday morning, the campaign group said: “Today we will disrupt one overground line as part of our escalating campaign to demand the government acts now on the climate and ecological emergency.”
London Mayor Sadiq Khan urged protesters to “think again”, adding public transport helped tackle climate change.
Music student Anouska Stahlmann said her ill mother and elderly grandparents were forced to walk part of their journey to avoid risking being stuck in a Tube tunnel.
The 20-year-old said: “I have no issue with wanting to better the environment and we’re fairly conscious of it as a family.
“Their methods, however, are seriously flawed and are not inclusive of people who want to support the cause.”
Protester and climate lawyer Farhana Yamin, who was arrested on Tuesday, earlier told BBC Radio 4’s Today programme: “I totally want to apologise to people using public transport.
“But at the same time we need to take actions that are disruptive so everyone understands the dangers we’re facing right now.”
Jace Tyrrell, chief executive of the New West End Company, said the West End lost £12m in trade because of the first two days of protests.
He told BBC Radio London: “Everyone has a right to peaceful protest. But this is really disruptive.”
In Edinburgh, dozens of people were arrested earlier this week when hundreds of protesters blocked a main road.
Organisers said protests had been held in more than 80 cities across 33 countries and action in London was planned until 29 April.
Three men and two women, in their 40s and 50s, arrested on suspicion of criminal damage at Shell’s headquarters in London on Monday, have since been released while inquiries continue.
What is Extinction Rebellion?
Since the group was set up last year, members have shut bridges, poured buckets of fake blood outside Downing Street, blockaded the BBC and stripped semi-naked in Parliament.
It has three core demands: for the government to “tell the truth about climate change”, reduce carbon emissions to zero by 2025, and create a citizens’ assembly to oversee progress.
Controversially, the group is trying to get as many people arrested as possible.
But critics say they cause unnecessary disruption and waste police time when forces are already overstretched.
The government said it shared “people’s passion” to combat climate change and “protect our planet for future generations”.
The Department for Business, Energy and Industrial Strategy said the UK had cut its emissions by 44% since 1990.
A spokesman said: “We’ve asked our independent climate experts for advice on a net zero emissions target and set out plans to transition to low emission vehicles and significantly reduce pollution.”