Dozens of petrol bombs were hurled at police vehicles during a republican parade in Londonderry.
Heavy masonry was used to smash the windows of Police Service of Northern Ireland (PSNI) vehicles in the nationalist Creggan estate.
Flames also ignited around the heavily armoured whitewashed Land Rovers.
Sporadic trouble continued for around two hours on Monday.
Republicans mark the anniversary of the 1916 Easter Rising every year.
Police warned demonstrators that it was an illegal parade.