British police arrested nine people after clashes between anti-immigration groups and anti-racism protesters in Dover on Saturday, with media reports of smoke bombs and bricks being thrown.
Groups such as the National Front confronted activists rallying against racism, such as the Kent Anti-Fascist Network, resulting in disturbances in the port town that lies 20 miles by sea from France.
Kent Police said one person suffered a broken arm and five people sustained minor injuries during the demonstrations, as BBC television footage showed dozens of hooded protesters pushing through police lines.
Britain's government is trying to curb rising levels of immigration from both EU migrants and arrivals from elsewhere in the world, over fears about the strain on public services.
Dover is symbolic as the entry point for many new arrivals. It is a short ferry or train journey from Calais in France, where thousands of refugees fleeing war and poverty in Africa and the Middle East have gathered over the past year, using it as a stopover point before trying to enter Britain.
Kent Police said three arrests were made in Dover itself and six at a nearby motorway service station.
"Extra officers were on duty in the town to allow a march to the Eastern Docks and a separate protest in the town centre to go ahead as planned, while minimising disorder and disruption to the community," the police said in a statement.