Violence broke out and missiles were thrown at police as rival protesters gathered in Leicester for rival demonstrations.
The English Defence League (EDL) and Unite Against Fascism (UAF) were holding protests in Leicester, prompting the city's largest policing operation in 25 years.
Around 1,000 members from each group were expected to descend on the city, police said, although it was not known exactly how many had turned up.
A smoke bomb was thrown from the EDL protesters into police and crowds of press.
Leicestershire Police said: "Officers are dealing with minor disorder among the EDL supporters on Humberstone Gate East. So far a number of protesters have been detained for possible public order offences."
Earlier this week, Home Secretary Theresa May authorised a blanket ban on marches in Leicester, but the groups were still permitted to hold static demonstrations in Humberstone Gate East in the city from 2pm to 3.30pm.
The area was shut down by police, with rival groups placed either side of metal barriers.
Police were using Section 14 of the Public Order Act which meant officers could take action against anyone who protests outside that place and time. They were also using stop and search powers, and were supported by the dog unit, mounted unit and East Midlands Air Support Unit.
At one point a policeman was put into a buggy-style ambulance on a stretcher. Some EDL protesters were also treated by police medics, but it is unclear what their injuries were.
A spokeswoman said: "Crowds remain and continue to protest. Four people have been arrested. One officer has been taken to hospital with a leg injury."
Violence broke out and missiles were thrown at police as rival protesters gathered in Leicester for rival demonstrations.
The English Defence League (EDL) and Unite Against Fascism (UAF) were holding protests in Leicester, prompting the city's largest policing operation in 25 years.
Around 1,000 members from each group were expected to descend on the city, police said, although it was not known exactly how many had turned up.
A smoke bomb was thrown from the EDL protesters into police and crowds of press.
Leicestershire Police said: "Officers are dealing with minor disorder among the EDL supporters on Humberstone Gate East. So far a number of protesters have been detained for possible public order offences."
Earlier this week, Home Secretary Theresa May authorised a blanket ban on marches in Leicester, but the groups were still permitted to hold static demonstrations in Humberstone Gate East in the city from 2pm to 3.30pm.
The area was shut down by police, with rival groups placed either side of metal barriers.
Police were using Section 14 of the Public Order Act which meant officers could take action against anyone who protests outside that place and time. They were also using stop and search powers, and were supported by the dog unit, mounted unit and East Midlands Air Support Unit.
At one point a policeman was put into a buggy-style ambulance on a stretcher. Some EDL protesters were also treated by police medics, but it is unclear what their injuries were.
A spokeswoman said: "Crowds remain and continue to protest. Four people have been arrested. One officer has been taken to hospital with a leg injury."