Three people were arrested and weapons including a knife, knuckle duster and hammers were seized after far-right protesters clashed with anti-fascist groups at an anti-immigration rally in Dover.
There was a heavy police presence in the seaside town as flag-waving demonstrators from the National Front and the right-wing South East Alliance marched to protest against the arrival of immigrants on Saturday.
Left wing activists from the Kent Anti-Racism Network organised a counter-demonstration, to which international development international development secretary Diane Abbott gave a speech before the march, and bricks and smoke bombs were thrown amid violent scenes as officers in riot gear and dog handlers struggled to keep order.
At one point officers were pushed back by left-wing activists in black hooded tops and with covered faces who broke through their lines.
One person suffered a broken arm during the protests and five others were injured, though not seriously, Kent Police said. Another man reportedly had a brick thrown at his face.
A female reporter for LBC who was covering the protest said that one far-right demonstrator threatened her, telling her she should be raped and that she should not be able to have children.
Three men were arrested for public order offences, breaching the police and possession of an offensive weapon.
Earlier, Maidstone services on the M20 were closed at around 11am after several coaches believed to be taking people to the protest were damaged.
Six people were injured and two coaches had swastikas painted on them in blood. One had its windscreen smashed as rival groups clashed.
Six men aged between 25 and 53 were arrested on suspicion of violent disorder.
Police activated "stop and search" powers in Dover on Saturday and seized a variety of weapons in the town and at the motorway services.
A spokesman said: "More than 20 weapons were seized in total at Dover and the M20 services, including a lock-knife, knuckle duster, poles adapted to cause harm, pieces of wood, glass, hammers and bricks.
"Kent Police would like to thank the local community for its cooperation and patience throughout the demonstrations."
Before the demonstration the South East Alliance II, which describes itself as an "angry, white and proud" street movement, advertised the protest on its Facebook page, saying: "Remember we are there for a purpose. To highlight certain issues we face. We are not there to have a kick-off with the red scum but we do know they will attack us and we shall defend ourselves without hesitation."
And following the march the National Front posted on its own Facebook site, saying: "A big well done and thank you to all white nationalists who attended Dover today to save our country from invasion. Respect to all in attendance."
Around 120 members of Britain First also held a demonstration in Dewsbury, West Yorkshire, while 80 people held a counter-protest nearby in the town.
No arrests were made but one man was detained earlier on Saturday for assaulting a police officer at Dewsbury train station.
Four men were also arrested at Barnsley railway station by British Transport Police for racially aggravated public order offences, in connection with the Dewsbury event.