Nineteen men aged between 13 and 19 have been released on bail by police investigating a series of brawls in London's Trafalgar Square on Thursday.
Knives, hockey sticks and other weapons were used as tourists and commuters looked on, police said.
A man aged 19, stabbed in the head, arm and back and a 19-year-old who received wounds to the neck, back and leg, have been discharged from hospital.
A 17-year-old stabbed in the chest is in a stable condition.
Eyewitnesses said young men were lashing out on the pedestrianised area around Nelson's Column and also on adjoining streets between 1600 and 1730 GMT.
Officers are studying recordings from several CCTV and traffic cameras located around the square.
The incidents are believed to be linked to Kosovo National Day celebrations.
"This appears to have been a spontaneous incident and our officers were on scene extremely quickly," said Superintendent Simon Ovens of the Metropolitan Police.
On Friday evening all of those arrested were bailed to return on various dates in the middle of April.
Police have urged anyone with information about Thursday's events to contact its investigation team.