Some transport routes in other British cities came to a standstill, with demonstrators chaining themselves together in Birmingham and Nottingham. More protests were planned in Manchester.
The UK-wide protests mark five years since 29-year-old black man Mark Duggan
was shot and killed by police in north London. His death sparked riots across the capital and other British cities.
"In the UK, families have in some cases been waiting decades to find out what's happened to their loved ones who have died in custody, or to get a straight answer -- even where wrongdoing has been found to be by police officers," Black Lives Matter UK spokesman Wail Qasim, 23, told CNN.
"So this demonstration comes after a decade-long struggle and it's to highlight what's happening."
Starting around 8:20 a.m. (3:20 a.m. ET), several demonstrators began chaining themselves together and lying across the M4 motorway leading to Heathrow Airport beneath a banner reading: "This is a crisis."
Ten people were arrested, said London's Metropolitan Police.
The airport is Britain's largest
, handling more than 205,000 passengers daily with 80 airlines traveling to 84 countries.
Between 200 and 300 people gathered in Altab Ali Park in the London neighborhood of Whitechapel to hear calls for unbiased treatment for people of color.
Transit was not shut down. Police maintained a discreet presence in the park but several police vans were parked on nearby streets with reinforcements if necessary.
The park was named after a Bangladeshi man killed in a 1978 racially motivated killing.
Members of the group also blocked roads near Birmingham Airport, in England's West Midlands region.
In Nottingham town center, in the East Midlands region of England, protesters also lay across tram lines, bringing transport to a standstill.
Four people were arrested at the protest, said Nottingham Police.
What is Black Lives Matter UK?
Black Lives Matter UK is a coalition of activists working under the Black Lives Matter banner and is not an official branch of the original US organization.
The groups do not share funding, however they are in contact and promote each other's events on social media.
"At the moment we're in conversation about how we might work together in the future," Black Lives Matter UK spokeswoman Shanice Octavia, 23, told CNN.
"They're very supportive because they understand that police brutality of black people is a global issue requiring a global response."
She added that Black Lives Matter UK is mostly made up of black people in their 20s but also includes those "from an older generation who have struggled against injustice in the past."
How global is Black Lives Matter?
In the United States, the police shootings of Alton Sterling in Louisiana and Philando Castile in Minnesota
last month sparked hundreds of protests across the nation -- and similar rallies worldwide.
Hundreds of protesters
filled the streets of London, Berlin and Amsterdam in solidarity with the U.S. Black Lives Matter movement.
"We've also seen recent cases of mobilized protests coming from the aboriginal community in Australia, and in Italy and France against black deaths in police custody," said Octavia.
The UK organization has also been protesting British immigration policies, pointing to the deaths of migrants attempting to reach the country.
Who was Mark Duggan?
Five years and one day ago, Duggan, a father of four, was shot by police officers who stopped the taxi in which he was traveling.
A 2014 inquest into his death found Duggan was lawfully killed, even though he did not have a gun in his hand at the moment he was shot.
The jury said it was more likely than not that just before he was killed, Duggan threw a gun from the taxi onto a grassy area near the scene.