Four people, including a 13-year-old girl, were arrested Saturday during a yellow vest pro-Brexit march in central London.
Around 100 people in yellow vests marched through Westminster towards Trafalgar Square, causing disruption and setting off smoke bombs.
The group's yellow vest outfits are similar to those worn by protesters in France during recent demonstrations.
British police said the 13-year-old girl had been arrested on suspicion of assaulting police.
Three men were also arrested on suspicion of public order offences, police said.
Video footage showed people sitting down in the road to stop traffic while other video footage posted online captured smoke bombs being let off.
This confrontations with police were also recorded and shared online, Xinhua news agency reported.
Earlier in the day, Transport for London warned people there would be disruption caused by the protest.
There were traffic delays in Westminster and towards the Regent Street and Piccadilly Circus areas.
There were also similar gatherings of people wearing yellow vests in Cardiff and Manchester, according to media reports.
