LONDON — Black activists, responding to calls for a nationwide protest against racial injustice, staged demonstrations in London and several other cities across Britain on Friday, in their boldest show of support to date for the emerging Black Lives Matter movement here.

Black Lives Matter U.K. had called for a nationwide “shutdown” to protest an array of injustices, including police brutality; racial disparities in arrests, convictions and sentencing; the treatment of immigrants in detention; inadequate mental health services; and a reported increase in hate crimes since Britain’s decision, in a June 23 referendum, to leave the European Union.

“We are here because we have no choice,” Wail Qasim, an activist and journalist who took part in a protest near Heathrow Airport, which serves London, wrote on Twitter. “We are here because this is a crisis.”

The Black Lives Matter movement, which emerged in the United States in 2013, has spread to several countries, including Britain, Canada and France.

So far this year, the police in Britain have shot and killed two people, compared with 571 in the United States.

On Friday morning, activists unfurled a giant banner and lay down on an access road near Heathrow, bringing traffic to a standstill for several hours. The police arrested 10 people.

Five more people were arrested in Birmingham, Britain’s second-most populous city, after blocking traffic leading to the airport. Four activists were arrested in Nottingham, a city of more than 300,000 in the Midlands, after protesters blocked trams and buses by lying down in front of the Theatre Royal.

The demonstrations were peaceful but powerful; in several cases, the authorities had to use special equipment to cut through the tubes the protesters had used to link their arms.

The demonstrations were timed to coincide with the fifth anniversary, on Thursday, of the fatal police shooting of Mark Duggan, a 29-year-old unarmed black man, in the Tottenham section of London. His death touched off riots in poorer sections of the capital, as well as in cities including Birmingham, Bristol and Liverpool.

In January 2014, an inquest jury found that the killing of Mr. Duggan had been justified, finding it more likely than not that he had tossed a firearm from a taxi shortly before he was shot. But in October, a judge granted Mr. Duggan’s family the right to appeal those findings.

The 2011 riots echoed disturbances that shook the Brixton neighborhood of London no fewer than three times — in 1981, 1985 and 1995 — in response to anger at police treatment of black residents.

In the U.K. we have exactly the same problems as in America, but in America they’re far worse.

Kehinde Andrews, associate professor of sociology and head of the black studies program at Birmingham City University
The activists have been upset by three recent deaths of black Britons: Mzee Mohammed, 18, who died last month after he was arrested in Liverpool; Sarah Reed, a 32-year-old with a history of mental illness, who died in a jail in North London in January and had previously been the victim of police brutality; and Jermaine Baker, 28, who was fatally shot by the police in North London in December, after he tried to free a convict from a police van.

“In the U.K., we have exactly the same problems as in America, but in America they’re far worse,” Kehinde Andrews, an associate professor of sociology and head of the black studies program at Birmingham City University, said in a phone interview. “You’re three times more likely to be killed by the police if you’re black, but the police don’t kill that many people in Britain in general.”

So far this year, the police in Britain have shot and killed two people, compared with 571 in the United States.

Britain has the largest prison population in Western Europe, and blacks are overrepresented. But even so, the incarceration rate is far lower than in the United States. Gun violence is also relatively rare in Britain; handguns were effectively prohibited after a 1996 massacre at a school in Scotland. Most police officers in the country do not carry guns.

Because deadly encounters with the police are fairly rare, activists in Britain have tended to focus more on the treatment of black people in custody, like Sean Rigg, a 40-year-old musician who had schizophrenia and who died in a police station in Brixton in 2008; and Kingsley Burrell, a 29-year-old student who died in police custody in Birmingham in 2011.

Hundreds of Black Lives Matter protesters demonstrated in London last month after the police shootings of black men in Louisiana and Minnesota.

When she took office as Britain’s prime minister on July 13, Theresa May pledged to fight “burning injustice” and to “make Britain a country that works for everyone,” noting that “if you’re black, you’re treated more harshly by the criminal justice system than if you’re white.”

In her previous position, as home secretary, Ms. May reduced the prevalence of “stop and search” (what Americans call “stop and frisk”), a policing practice that she denounced as ineffective and unjust, saying that people were often subject to scrutiny on no other basis than their skin color.

But Gus John, a black educator and activist who immigrated to Britain from Grenada as a young man, described Ms. May’s speech as “a bit rich,” noting that she was in charge of domestic security and policing when Mr. Duggan died.

“If society tacitly endorses racial injustice, and doesn’t see the matter as one that faces the country as a whole but simply as episodes that the black community has got to deal with, it is not just legitimate but necessary to take the struggle to them,” Mr. John said, adding that he “absolutely” supported the protests.

Blacks account for about 3 percent of Britain’s population, compared with nearly 13 percent in the United States.

While people of African origin have lived in Britain for centuries, large-scale black migration began with people from the Caribbean after World War II, followed by an influx from former British colonies in Africa, especially Ghana, Kenya, Nigeria, South Africa, Uganda and Zimbabwe.

Originally published on the New York Times