Two people have been arrested on suspicion of assault and causing criminal damage after rival groups clashed in County Londonderry.
Damage at the scene of the trouble
The loyalist occupants of a minibus returning from a football match and about 30 local people were involved in the violence near Maghera on Monday.
The trouble followed an incident at a republican mural at Glenshane Road.
Three men were assaulted, a car was damaged and all but two windows of the minibus were smashed, police said.
A police officer suffered minor injuries when he was struck by a missile thrown from the crowd and a police vehicle was also damaged.
The two people who were arrested were released on bail to appear in court at a later date.
Several people were treated in hospital following the trouble.
PSNI Chief Inspector Paul Douglas said, "People need to show more respect for the traditions and cultures of others and also need to find better ways of resolving their differences without resorting to violence."
It is understood a group of loyalists travelling to Londonderry in the minibus damaged a hunger strike billboard in a nationalist area.
There are claims that a farmer who intervened was threatened and assaulted and a family living on the Glenshane Pass were assaulted in their home.
Martin Molloy, who lives in the area, was with the family shortly after the incident at their home.
"The mother was hurt. The two fellas seemed to be severely hurt. Their faces were very badly bruised and the fellas were in shock," he said.
Following the violence, police escorted the minibus to Magherafelt police station.
MP for mid-Ulster Martin McGuinness, Sinn Fein, visited the family involved on Tuesday.
He condemned what had happened and described the performance of police as "dismal and incompetent". Mr McGuinness also appealed for calm.