Youth activists have taken the Extinction Rebellion protests to Heathrow on the fifth day of action, demonstrating beside the main roundabout on the road to the airport.

The activists, all born after 1990, unfurled a banner asking: “Are we the the last generation?” as dozens of police prevented them from blocking the road.

The protesters said they were risking arrest to highlight the dangers of climate change. “To everyone reading about this, I’m here because I love you and fear for your future and my future,” said Oscar Idle, 17, from Bristol. “It’s that love and that fear that gives me courage.”

About 20 protesters were moved on to the pavement by police at one of the road entrances to the airport. Protesters stood by the tunnel that leads to terminals two and three, but all roads around the roundabout were open and there was no disruption to motor traffic as the group remained surrounded by police.

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

About 25 police, some of them reportedly brought in from Cardiff and other regions, repeatedly warned the teenage protesters they could be arrested if they did not move on, but four of the activists refused to budge for more than an hour.

The representatives of Extinction Rebellion Youth, which operates with some autonomy from the wider organisation, said they never planned to disrupt flights, though they had planned to block traffic intermittently. Several among the group chanted “People power” and: “We are the youth and we’re doing what’s right. We are the youth and we are fighting for our lives.”

Some were in tears but held their ground. They said they were crying as much because of the climate crisis as the stress of the standoff. “We are consistently being punched in the face by the truth, but nobody is doing anything,” said Savannah Lovelock, a 19-year-old student from the University of Falmouth. “I just want to go home. But we have no choice. If other people stood up for the next generation, we wouldn’t have to.”

“I shouldn’t be here, I should be revising for my end-of-year exams,” said Talia Woodin, 19, who is at Goldsmiths. “But I have to be here. What good is a degree if there is a possibility that there is no future?”

“We know the risks and they are worth taking. I’m incredibly proud to be here with the others,” said Samar, 14. “We’re facing a complete disaster and I refuse to stand by and watch this happen without doing something.”

At about 10am, the four activists moved on, holding hands with their arms raised.

The action came as the number of arrests from Extinction Rebellion’s week of protest passed the 500 mark. Despite the detentions, activists have held roadblocks at four locations in central London since Monday and expect more to join them on Friday, the start of the Easter weekend holiday.

They believe the BBC programme Climate Change: the Facts, which aired on Thursday night, will strengthen their cause.

“The David Attenborough documentary will have a huge impact,” predicted Ronan McNern, a spokesman for Extinction Rebellion. He said the group’s disruptions over the past six months were shifting the debate. “We are creating conversations. For the first time people are talking at the breakfast table, in pubs and on the tube about the climate crisis. That’s what this is all about.”

They have been boosted by wide media coverage and endorsements from prominent figures in the science community and 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”.

Actor Emma Thompson joins the activists in London. Photograph: Tolga Akmen/AFP/Getty Images

The latest high-profile supporter is the actor Emma Thompson, who joined the Oxford Circus camp on Friday morning. Hundreds of people sat in the street and listened to poetry readings. When dozens of police officers moved in to try to disperse them, Thompson – who was on top of a boat in the middle of the junction – joked: “I want to remind the police that Nanny McPhee is up here, and I have my stick with me.”

The home secretary, Sajid Javid – considered a contender in the Conservative party’s leadership race – called for police to use “the full force of the law” against the demonstrators.

On Thursday night the Metropolitan police said they had cancelled leave for some officers over Easter.

“This is putting a strain on the Met and we have now asked officers on the boroughs to work 12-hour shifts; we have cancelled rest days and our violent crime taskforce have had their leave cancelled,” the force said in a statement.

The 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.”