Six Extinction Rebellion activists have been arrested after members of the group chained themselves to the entrances of a concrete factory in east London.

Around 50 protesters blocked the gates to London Concrete – the capital’s biggest supplier of ready-mixed concrete and which is supplying the £1bn Silvertown Tunnel project being built under the Thames. The works in Bow is planning to expand to meet demand for concrete.

Activists said the protest was to highlight the “devastating effects the expansion will have on the health of local residents”.

The blockade comes as the group has launched five days of non-violent protests in five cities across the UK, urging the government to implement major policies to tackle the worsening climate crisis.

Dozens of activists held a banner saying: “The air that we grieve”.

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Others chained themselves to metal pipes and prevented any vehicles and workers from entering the site.

“Concrete has a huge environmental impact and building another tunnel will only make air pollution across East London worse,” said spokeswoman Eleanor McAree.

The 25-year-old added: “Air pollution is already at dangerous levels and is affecting the health of children and adults in the area.”

Tower Hamlets’ resident Morgan Trowland, a 36-year-old structural engineer and member of Extinction Rebellion, said: “I’m taking part in this action to disrupt concrete production, because we have to pause and recognise the harm it is causing both locally and globally; locally with the dust in the air our children breathe and globally with the inextricable CO2 emissions involved which are destroying the world.”

Police said the protest had prevented companies in the area from going about their business and officers had arrested six people aged between 30 and 67 on suspicion of aggravated trespassing and obstruction of a highway.

London Concrete is a unit of Franco-Swiss group LafargeHolcim. The Silvertown Tunnel under the Thames will link the Greenwich Peninsula and Silvertown.

Extinction Rebellion wants non-violent civil disobedience to force governments to cut carbon emissions and avert a climate crisis it says will bring starvation and social collapse.

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“We absolutely recognise the right for people to protest however we will continue to take action against those who choose to break the law, to ensure disruption to Londoners is kept to a minimum,” said Commander Jane Connors of London's Metropolitan Police. “We are aware that protesters are expected to target the construction industry this week.

We are engaging with business across the capital.”

In April this year Extinction Rebellion activists disrupted London with 11 days of protests the group described as the biggest act of civil disobedience in recent British history.