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Anti-racism activists brought traffic to a standstill on the road to Heathrow airport on a day of action which featured protests around the UK.
Campaign group Black Lives Matter - or BLMUK - said it wanted to commemorate the fifth anniversary of the death of Mark Duggan, who was shot by police attempting to arrest him in Tottenham, north London, in August 2011, sparking nationwide riots.
The group called for "nationwide #shutdown" in a post on social media, and their Friday morning protests resulted in a number of arrests.
The activists said they had shut roads in London, Birmingham, Manchester and Nottingham to "mourn those who have died in custody and to protest the ongoing racist violence of the police, border enforcement, structural inequalities and the everyday indignity of street racism".
Pictures posted on Twitter showed protesters lying in a row across the M4 slip road to Heathrow beneath a banner which said: "This is a crisis."
Video footage showed police officers hunkering down next to the protesters, while chants of "black lives matter" could be heard as some people got out of their vehicles, which were bumper-to-bumper on the road into one of the world's busiest airports.
Nottinghamshire Police said officers were negotiating with a small number of protesters, and photographs posted on Twitter showed four activists lying across tram tracks in the city of Nottingham.
Footage of the protest near Birmingham Airport showed police officers pulling demonstrators away from the middle of the road.
Scotland Yard said a number of people were arrested at the Heathrow incident, while West Midlands Police said four women and one man were arrested on suspicion of obstructing the highway and failing to comply with section 14 of the public order Act on the A45 in Solihull.
A spokesman for Nottinghamshire Police said screens erected at the scene of the protest were to prevent distraction for motorists.
Screens were also at the scene of the Heathrow incident, where video footage appeared to show a number of police officers moving the protesters while they continued to lie on the road.
The day of action comes just a day after the anniversary of Mr Duggan's death. An inquest jury decided that Mr Duggan was lawfully killed by a police marksman.
A video on the BLMUK Facebook page features a man saying there have been "1,562 deaths in police custody in my lifetime", adding that there have been zero convictions.
Another man says black people are "up to 37 times more likely" to be stopped and searched, while another says black people face "far more severe" sentencing than white people for the same offence.
Meanwhile, the number of fatal police shootings in the US has led to widespread condemnation.
In recent weeks, two white officers in Baton Rouge, Louisiana, killed a black man during a scuffle and an officer in Minnesota shot and killed a black motorist during a traffic stop, sparking protests.
Police have also been the victims of fatal shootings, with five officers killed in Dallas, Texas, and three law enforcement officers gunned down in Baton Rouge.
BLMUK describes itself as a network of anti-racist activists from across the UK.
The group said: "We stand in solidarity with the families and friends of all who have died at the hands of the British state. We take action because justice has not been delivered through conventional means: the police, the IPCC, the courts or the legislature."
The campaigners said they aim to highlight "the struggle for black lives in the UK and £Shutdown state-sanctioned racialised sexism, Islamophobia, classism, ableism, homophobia and transphobia", adding: "We fight for liberation.
Nottinghamshire police have said they are aware of disruption in the city, where protesters are lying across tram tracks.
The force said officers are at the scene negotiating with a small number of protesters.
A Heathrow spokesperson has said they are not aware of any flight cancellations as a result of the protest.
They said they had no information on whether flights would be delayed.
The airport is advising people driving to Terminal 2 and 3 to consider alternative transport.
Campaigners have also called for a demonstration in London, beginning at 6.30pm.
A spokesman for Nottinghamshire Police says screens erected at the scene of the protest are there to prevent distraction for motorists.
Screens are also at the scene of the Heathrow protest.
Organiser Joshua Virasami has told the BBC that the Black Lives Matter movement was needed “in Britain and all over the world.”
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