Protesters from the Black Lives Matter movement have blocked road access to Heathrow Airport this morning.
Acitivists reportedly chained themselves to the roundabout leading into Heathrow, blocking the M4 and stopping vehicles from driving into the airport grounds.
Twitter user Hannah said the M4 has been "shut down" due to the protest.
Sky News reported that six protesters have locked themselves to boxes blocking lanes lead the the airport entrance.
Metropolitan Police said a number of people were arrested at the scene, and one lane of traffic has been opened, but there is ongoing traffic congestion as a result of the demonstration.
One Twitter user posted a video of the demonstrators and the traffic brought to a standstill, before the arrests were made.
"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," a Heathrow spokesperson said.
"We are sorry to those passengers whose journeys are being disrupted and we are working with the authorities to resolve the issue."
The protest is not believed to be related to issues with the airport.