July Twelfth is the traditional Orange Order marching day when they celebrate King William’s victory at the Battle of the Boyne.
According to UTV News a number of police officers were taken to hospital with suspected broken bones, and head and neck injuries after being attacked with ceremonial swords, bricks, bottles and huge pieces of masonry.
Hundreds of police officers were drafted to Northern Ireland from around the UK to deal with the violence.
More than 49 people aged between 15 and 52 were arrested during the disturbances after Orangemen were prevented from walking along a 300m stretch of road which passes a nationalist area of north Belfast on Friday night.
“It was visceral. If you watch the footage of some of those people involved in attacking police lines on Friday night, particularly on Woodvale Road, their behaviour was almost animalistic,” Police Service of Northern Ireland Assistant Chief Constable Will Kerr said on Monday.
Kerr said the policing bill had already run into multiple millions of pounds.
He added: "It was incredibly dangerous to engage in that sort of behaviour so quickly at police lines. The police officers who held the line at Woodvale Road and who continue to hold the line have shown incredible professionalism."
During the police press conference on Monday a number of riot squad helmets were on display, including one which was dented by a ceremonial sword.
At least four blast bombs and several petrol bombs were thrown at police in the Lower Newtownards Road area of east Belfast.
The Belfast Telegraph reports that water cannons were deployed and plastic bullets fired.
In the Ardoyne area of north Belfast, a pipe bomb was thrown at police patrolling the area, at around 5pm on Monday.
Commenting on the incident, Superintendent Emma Bond said: "We consider ourselves extremely fortunate that we are not dealing with a much more serious incident and that all of the officers were able to walk away from that situation unharmed.
"We have appealed for calm in the area and I continue to to do so. I would appeal to anyone with influence in the community to exert it to ensure that the next few days pass off without incident."
Meanwhile the Orange Order said the PSNI had questions to answer about how officers handled the situation.
A statement said: "The PSNI have serious questions to answer, not least, with so many police officers available, why were they unable to stop clearly orchestrated attacks, and, in the case of the Short Strand, a prolonged attack lasting over 30 minutes along the length of the peace wall?
"The violence, which we condemn, cannot be used as an excuse for not addressing the issues that have been raised by this ludicrous determination.
"There will be the blame game and point-scoring by all for the events that unfolded; however, the Orange institution will be scapegoated for where the responsibility for this crisis truly lies - at the door of the Parades Commission."
Watch the UTV News report here