Two police officers were injured after having bottles thrown at them during a nationalist march.
Missiles were hurled during the fifth annual March for England gathering in Brighton, East Sussex, which attracted counter demonstrations by anti-fascist protesters.
The two injured officers, both male constables, received head injuries during tense scenes, with one being admitted to hospital for treatment before later being discharged.
Heated exchanges were traded between marchers and protesters in the seaside city after the 140-strong march set off by Brighton railway station.
Mounted police were drafted in to maintain calm as attempts were made to obstruct the march at several points amid "considerable levels of violence", Sussex Police said.
Three people were arrested on suspicion of public order offences.
And several police horses received cuts and grazes after being attacked by protesters, but there were no reports of damage to property or injuries to members of the public.
Superintendent Steve Whitton, of Sussex Police, said afterwards: "A strong police presence was necessary in order to ensure that the event took place and the risk of disorder and injury was minimised.
"We had several hundred officers available, with support from surrounding forces including mounted officers, and our priority throughout was on public safety whilst at the same time enabling both the marchers and counter-protesters to express their views within the law."
He added: "Our priority throughout the day has been ensuring public safety whilst allowing peaceful protest, minimising disruption to the city, local communities and businesses, preventing crime and disorder and providing a safe and secure environment for the protesters and the surrounding community.
"However, we were concerned that there were some people at this event whose intention was not to peacefully protest.
"We were able to restrain these groups and individuals with a firm, robust but fair policing response, but this did require a major police presence at several points."
Matt Silva, a spokesman for March for England, said he was "completely appalled" at the level of violence directed at his members, saying women and children had missiles thrown at them.
He said there was no provocation from any of the marchers who sang the national anthem because it was the Queen's birthday on Saturday.
He added: "From my side, we did all we could to facilitate a peaceful and lawful gathering.
"There was no provocation, no racial chants, no homophobic chants which we have been accused of doing in the past. This was a family event but I was completely appalled at what we saw. There was no excuse for the violence."
Lou Kenton, from the Anti Fascist Coalition, told the BBC: "Every year they parade through Brighton and shout fascist abuse at passers by."