A teenage boy and a man in his 20s have been taken to hospital for injuries sustained during disorder in Londonderry on Friday night.
At around 19:00 BST police were made aware of two large groups of rival football supporters in the Lecky Road and Lone Moor Road area.
They were attacking each other with sticks, bats and iron bars and causing damage to buildings and cars parked in the area, police have said.
Further disorder also occurred during and after a match between Derry City and Bohemians at the Ryan McBride Brandywell stadium in Londonderry.
The Police Service of Northern Ireland said they believed the disorder was “pre-arranged”.
Footage of the incident posted on social media appears to shows fans ducking and running as the fireworks explode around them.
Social Democratic and Labour (SDLP) assembly member Mark H Durkan was at the match and said the event was “ruined by violence and the fear of violence” for many genuine fans.
He also said a flare landed on the pitch during the game which briefly stopped play.
Durkan told BBC News NI that because of concerns about violent incidents which had happened elsewhere in the city before the match, stewards put in place a “safe exit” plan for supporters’ buses.
He said he had been speaking to police officers during the event to ask them about their plans “to minimise the risk of bother after the match”.
However, as the Foyle assembly member left the Brandywell he witnessed a crowd of about 60 fans who “ignored” the stadium workers’ instructions.
Durkan said these people “overran the stewards” in order to get out of the car park and they ran down Lone Moor Road “hell-bent on causing more trouble”.
“The vast majority of people I’m sure were here for the football, others had come to fight. It’s really just disgusting,” the assembly member added.
Officers were in attendance and worked along with stadium staff to bring the disorder under control.
Police said no arrests have been made at this time.
Sinn Féin MLA Padraig Delargy condemned those behind the incident.
He said it was “terrifying for local residents, including children, who witnessed this appalling violence”.
“It threatened the safety and well-being of local residents and stands in stark contrast to the fantastic work that is going on in the area through the Féile and the redevelopment of Meenan Square,” Delargy said.
The game ended in a 1-1 draw.
BBC News NI has contacted Derry City FC and Bohemians FC for comment.
