Police in London said a group of protesters throwing missiles and bottles of bleach have marred an otherwise trouble-free May Day.
Around 15 people were arrested after sporadic evening disturbances across Soho, where police imposed cordons to contain demonstrators.
Five officers were hurt in the May Day protests, four with minor injuries and one had his arm broken when a fire extinguisher was thrown.
The other injuries are all thought to have been caused by protesters hurling missiles such as glass bottles and pieces of wood. One officer says protesters were throwing bottles of hydrogen peroxide across police lines.
Coffee shops and fast food outlets were targeted by some, with Starbucks, McDonald's and Costa Coffee outlets having windows smashed.
Up to 6,000 people gathered for the annual May Day anti-capitalism demonstration in Trafalgar Square.
The day's proceedings had earlier been described by police as "peaceful and good humoured". Police say around 300 people in the Soho area caused the last-minute violence.
PA