Six Northern Ireland police officers were injured Saturday as rioting erupted on the streets of Belfast.
What police called "significant disorder" flared following a Protestant march through the city Friday night, with police using water cannons and rubber bullets to try to disperse crowds.
Police say they came under attack from both Protestants and Catholics as they tried to keep the rival groups apart. Six officers received minor injures when they were hit by debris thrown by youths.
Authorities said seven people were arrested for disorderly behavior.
The rioting first erupted late last month after two nights of violence in which two people shot in the leg.
It is not clear what sparked the unrest, which comes at the start of the annual sectarian parade season.
Protestant loyalists in Northern Ireland want to remain part of Britain, while Catholic Republicans want to break free of British rule and join Ireland.
Some information for this report was provided by AFP and Reuters.