Five people were arrested after scuffles broke out as the English Defence League (EDL) and anti-fascists marched in Cambridge.
The number of people marching with United Against Fascism (UAF) and the TUC swelled from about 300 to 1,000 during the day, police said. About 350 people were on the EDL march, according to police.
More than 650 officers from six forces took part in the policing operation. Police said it was largely peaceful.
Those arrested were: a 36-year-old man from Norwich, on suspicion of being drunk and disorderly; a 48-year-old man from Colchester, Essex, on suspicion of a public order offence; a man aged 27 from Ely, Cambridgeshire, on suspicion of a public order offence; an 18-year-old man from Peterborough on suspicion of affray; and a man aged 28 from Cambridge, arrested on suspicion of a racially-aggravated public order offence.
Insp Robin Sissons said: "In the end it was a largely peaceful protest with only minor disorder and some minor disruption to residents, visitors and businesses in the city."