Eight men have been arrested on suspicion of public order offences after fighting broke out at a cycling event.
Some 30 protesters descended upon the Eritrean Cycle Festival at Curzon Ashton FC's Tameside Stadium in Greater Manchester where a number of objects were thrown and people were attacked.
Police attended the scene after they received reports of brawling at the stadium at about 3.15pm on Saturday.
Nine people, including two teenagers, suffered what are believed to be minor injuries.
The eight men arrested are being questioned in custody, said police.
It was reported the group of 30 were taking part in an organised protest against the Eritrean government in east Africa.
Chief Inspector Andy Harty, of Greater Manchester Police, said: "The vast majority of people attending the event today were innocent people, including children, who sadly got caught in the middle of this appalling act of violence.
"Following the fast work of officers a number of men were arrested at the scene and we will continue to question them as this investigation progresses.
"However, we are still in the very early stages of inquiries and we are keen to hear from anyone who witnessed this incident.
"In particular we would like people to come forward with phone or dash-cam footage that could be vital to finding all those responsible.
"This type of behaviour is completely unacceptable and I want to assure the residents of Tameside that we are doing everything we can to bring any offenders to justice."
Anyone with any information should call police on 101 quoting incident number 1417 of 16th June 2018. Alternatively, information can be passed on anonymously by calling the independent charity Crimestoppers on 0800 555 111.