There have been outbursts of sporadic violence in the North as Orange Order parades are taking place on the traditional marching day of July 12.
Two vehicles have been hijacked in separate incidents in North and West Belfast and are being examined by police.
In one of the incidents a city bus was hijacked by two masked men and left outside the gates of Woodbourne PSNI Station shortly after 4pm.
Meanwhile in Lurgan - around seven petrol bombs have been thrown and a train was attacked by youths but no injuries have been reported.
Politicians and police are appealing for calm.