LONDON - Climate-change activists disrupted rail services in London on Thursday, sparking a clash between angry commuters and a protester who had climbed onto the roof of a London Underground train during rush hour.

Extinction Rebellion is in the second week of a civil disobedience campaign that has targeted government buildings, an airport and financial institutions such as BlackRock to highlight the threat posed by global warming.

Protesters said they wanted to draw attention to the widespread loss of human life, mass extinction of species and threat to food supplies foreseen by scientists unless the world moves to cut carbon emissions and restore collapsing ecosystems.

"People are dying now because of the climate crisis and it threatens all we love," said Ruth Jarman, 56, from Christian Climate Action, who took part in the tube action.

The plan to halt trains was widely opposed by Extinction Rebellion supporters who feared that it would embolden the movement's critics and spark a backlash among Londoners.

Footage showed protesters unfurling a banner on top of a stationary train carriage at Canning Town before commuters on a crowded platform began hurling insults and pelting one of them with food.

The protester then tried to kick away a commuter who clambered onto the carriage. After a brief struggle the protestor was dragged to the platform, where he was swallowed by a crowd of people shoving and shouting before a woman and a member of the Tube staff intervened to restore order.

"The crowd became hostile very quickly due to wanting to go to work. I sympathise with the aims of Extinction Rebellion but this was an own goal," said Turan Basri, 57, an environmental health manager, who witnessed the incident.

"Canning Town is a very working class area. Seeing what they perceived to be middle-class protesters preventing working class people from earning a living didn't go down well," Basri said.

British Transport Police said eight arrests had so far been made at Canning Town and two other stations.

Police condemned the Extinction Rebellion action, but also expressed concern that members of the public had used "violent behaviour" to detain the train protester.

A spokeswoman for prime minister Boris Johnson said the protest caused "unnecessary disruption" and London Mayor Sadiq Khan condemned it.

Separately, small Extinction Rebellion groups held protests against the arms trade by glueing or locking themselves to the London offices of defence companies Leonardo UK , Lockheed Martin Corp and Britain's Supreme Court, the movement said. At least seven people were arrested.

Police said on Wednesday 1,642 people had been arrested after action targeting the Treasury, financial institutions and City Airport.

Extinction Rebellion says more than 1,400 of its supporters have also been arrested in 20 cities around the world since Oct. 7, including in New York, Brussels, Melbourne and Toronto.

The London protests could affect one of the city's maajor transport infrastructure projects.

Tim Clark, president of Dubai-based airline Emirates, said the upsurge in climate protests may prevent the construction of a third runway at Heathrow airport.

"With what’s going on in and around this city I sometimes wonder if this is going to get across the final hurdle, even though the government has legislated to do it,” Clark told delegates at Airlines 2050, an industry conference held in central London under tight security.

A coalition of local councils, residents’ and environmental groups and the mayor of London is currently pursuing a challenge against the Heathrow expansion through the appeals courts.

(Reporting by Andrew MacAskill, Paul Sandle, Kylie MacLellan, Laurence Frost and Matthew Green Editing by Kate Holton, Shri Navaratnam, Guy Faulconbridge, Mark Heinrich and Giles Elgood) ((Andrew.MacAskill@thomsonreuters.com; +447818584430; Reuters Messaging: andrew.macaskill@thomsonreuters.com))