Campaigners chanted “no justice, no peace” during a vigil for a black man who died after a police chase in east London.
Police said Rashan Jermaine Charles was followed on foot after officers tried to stop a car in Kingsland Road, Hackney, at 01:45 BST on Saturday.
He then tried to swallow an object but died later in hospital, they said.
Up to 150 campaigners blocked a road during the protest outside Stoke Newington Police Station.
Many held Black Lives Matters placards during the vigil organised by Stand Up To Racism.
Campaigners said they were “enormously concerned and angered” about the death of 20-year-old Mr Charles.
Ch Supt Simon Laurence, the Borough commander for Hackney, said officers “understand that they will be asked to account for their actions and they would not want it any other way”.
He said the death “has had an impact on some members of the local community” and police had met with community representatives “so we can hear the community’s concerns and how they are feeling.”
Scotland Yard said the officer involved “intervened and sought to prevent the man from harming himself”.
A force medic provided first aid at the scene before London Ambulance Service paramedics arrived.
Mr Charles was taken to the Royal London Hospital in east London and was confirmed dead at 02:55 BST.
The police watchdog, the Independent Police Complaints Commission, is investigating.
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