Police made 35 arrests and say more are likely after riots broke out in Birmingham city centre at the weekend.
Rallies by rival groups spilled over into violence in the main shopping area early on Saturday evening.
Bystanders ran for cover as protesters from the recently-formed group, Casuals United, said to consist of many football followers, and Unite Against Fascism clashed in New Street, just before 7pm.
Casuals United had organised a demonstration against Muslim extremism, but anti-fascists then staged a rival rally.
Three people were injured as hundreds of police, some clad in full riot gear, struggled to keep the peace. At one point officers were forced to seal off New Street with a steel barrier.
Witness Emily Bridgewater was shopping when violence broke out. She said: “It kicked off very suddenly and there was stampeding and screaming.
“We ended up being herded into Primark, where they brought the shutters down to protect us. It was very frightening.”
Photographs and video footage from the running battles are being studied by police who may now apply for injunctions to bar some of the troublemakers from the West Midlands.
Chief Insp Mark Payne, of West Midlands Police, said: “To date there have been 35 arrests - the majority for disorder, but this figure may increase as investigations continue into the incident.
“Officers were deployed throughout the city centre to manage two separate protests which took place during the course of the afternoon.
“Isolated incidents of disorder occurred when small groups of protesters broke away and actively sought to engage in criminal behaviour.”
He added: “The events are a very rare occurrence and normal city centre life resumed within a short space of time. I want to reassure all members of the community that the city centre is, and will continue to be a safe place to live, shop and visit.
“It is important to be aware that West Midlands Police have no powers to ban or stop peaceful protests and would not seek to do so. However, if criminal acts or racially aggravated incidents are reported, then police will arrest and prosecute anyone found to be responsible.”