Campaigners blocked a road during a vigil for a 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.
Following a vigil outside Stoke Newington police station, some people threw bottles and sticks at police and set fire to rubbish bins in the road.
A mattress was placed across the road and one protester's car was parked across the street, BBC reporter Andy Moore said.
Police were monitoring the situation and would intervene if necessary, The Met said.
A spokesman for the force said no officers had been injured.
Earlier people 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 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.
The police watchdog, the Independent Police Complaints Commission, is investigating.