Thousands of loyalists gathered in Belfast city centre for a protest against new restrictions on flying the Union flag.
A major security operation is under way to prevent more trouble breaking out at the demonstration in front of City Hall.
There was a heavy police presence in the area but the atmosphere was said to be calm and the crowds have already began to disperse.
Eight police officers were injured and more than a dozen people arrested during overnight clashes between loyalists and riot police.
PSNI Assistant Chief Constable Will Kerr earlier confirmed Loyalist paramilitaries have been orchestrating some of the violence seen in the past 24 hours.
He had appealed to those planning on going in to the city centre to protest to stay away and let people get on with everyday business such as Christmas shopping.
"We are also warning anyone who does engage in criminal activity that they will face the full rigours of the law," he said.
"Violence has serious and unwanted consequences for us all and we will robustly investigate all incidents."
"I am urging everyone to be calm, take a step back and think about how this violence is affecting not just their own communities but the whole of Northern Ireland."