AN illegal loyalist parade sparked a riot in Ballymena and the overnight closure of part of the M2 motorway, with further marches expected across the north over the next week.
Nine officers were injured after petrol bombs and masonry were thrown at police lines in the Co Antrim town on Monday night.
Police are investigating several illegal parades including in Portadown and Markethill in Co Armagh on Monday.
It is understood that further gatherings, similar to protests seen during the Union flag dispute of 2012/13 will be held in loyalist areas over the coming days.
While the Portadown and Markethill parades passed off peacefully, violence erupted when several hundred people took part in an illegal parade in the Ballykeel 2 estate in Ballymena at round 9.30pm.
Rioting broke out after Tactical Support Group officers moved in.
Debris including a wheelie bin was thrown on the M2 motorway during the riot.
Part of the motorway later had to be shut to allow the road to be cleared.
Police said the officers were expected to be able to return to duty yesterday.
In Portadown, a large group of men carrying flags paraded on Jervis Street in the town late on Monday afternoon.
And in Markethill, a large group of mainly young men gathered in the Co Armagh village's main street on Monday evening.
A loyalist band paraded up the street, filmed by a group of onlookers.
PSNI Chief Superintendent Davy Beck said it was fortunate no one was injured on the M2 during the violence in Ballymena.
"Not only did their reckless and criminal behaviour place the lives of our officers in danger, but such senseless behaviour shows the blatant disregard those responsible have for the safety of others by throwing debris onto a motorway," he said.
He added: "As your Police Service we are here to protect life and property and to keep people safe, and we will continue to do that.
"However, I am calling on all those who have influence to do what you can to bring an end to this violence as no one wants a repeat of these disgraceful scenes."
Following the parade in Portadown, Sinn Féin MLA John O'Dowd said the event was closer to a loyalist show of strength in Pitt Park in east Belfast in February than a march.
"Irresponsible and dangerous sabre rattling and reckless rhetoric from Unionist politicians has seen tensions rise right across the community," he said.
However, DUP MP Carla Lockhart blamed Sinn Féin for creating a political crisis following controversy over the policing of veteran republican Bobby Storey's funeral in Belfast last June.
"The chief constable must take responsibility for Sinn Féin receiving special treatment from the police whilst ordinary people were prosecuted," she said.
She added: "For my part, I will oppose law breaking in all forms. All lawbreaking is wrong. I urge those loyalists, frustrated by the actions of Sinn Féin, to step back. Remain peaceful and stay off the streets. We don’t want young lives criminalised. Two wrongs don’t make a right."
