Demonstrations are taking place in London, Birmingham, Nottingham, and Manchester
Ten supporters claiming to be part of the Black Lives Matter movement have been arrested during a demonstration near Heathrow Airport in London.
The British Metropolitan Police said four people had been taken to west London police stations, where they remain in custody.
Officers said a further six people were arrested at the scene and they are in the process of releasing the remaining activists who have "locked on" to each other while lying on the tarmac.
Screens have been put up to prevent distraction for motorists.
Video footage showed police officers hunkering down next to the protesters, while chants of "black lives matter" could be heard.
Scotland Yard said officers were called at 8.25am this morning to the M4 slip road at one of the world's busiest airports.
A spokesman said: "Officers have attended and a number of people have been arrested. One lane has been opened but there is traffic congestion. Police continue to deal with the situation at the scene."
Heathrow said the protest does not appear to be causing people to miss flights.
A spokesman said: "Heathrow supports the right to peaceful protest within the law, but the safety and security of our passengers, aircraft and colleagues, together with the smooth running of the operation, is paramount."
"We are sorry to those passengers whose journeys are being disrupted and we are working with the authorities to resolve the issue."
The disruption at Heathrow was part of wider demonstrations in other parts of the UK.
Protesters had called for a "nationwide #shutdown" in a post on social media on Thursday, with events also being held in Birmingham, Nottingham, and Manchester.
Members of the movement are also causing delays to the tram network in Nottingham city centre by lying on the tracks.
Nottinghamshire Police said officers are at the scene negotiating with a small number of protesters and screens have also been put up.
Earlier this morning during rush hour a group of protesters blocked the A45 in Solihull, and five people were arrested for obstructing the highway.
The group has said it staged the "shutdown" of roads 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".
The demonstrations come on the fifth anniversary of the fatal shooting of Mark Duggan by police in north London, which led to riots in several cities across England.
The 'Black Lives Matter' movement began in the US in protest against police killings of black people.
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.