Three people have been stabbed in Belfast as the city prepares for annual Twelfth of July celebrations.
Bonfires are traditionally lit in the North on the Eleventh Night, but the occasion this year coincided with sectarian conflict and fighting.
In one case, a gang of around 40 republicans and loyalists had to be separated by police.
Today marks the culmination of the loyal order marching season when thousands of members commemorate the victory of Protestant King William of Orange over Catholic King James II at the Battle of the Boyne in 1690.
Alliance Party assembly member Anna Lo said: “I am shocked that this sectarian fight has taken place in South Belfast. Those who took part should be ashamed of themselves.”
The victim, 28, was treated in hospital for injuries which are not believed to be life-threatening, police said.
They were received after republicans clashed with loyalists at a normally peaceful sectarian interface on the Ormeau Bridge in south Belfast in the early hours of this morning.
Police said overall disorder had been kept to a minimum, with a total of three stabbings reported and a further eight people arrested for public order offences in north and west Belfast. Five men were later charged with a variety of offences including rioting and assaulting police.
Six men were later charged with a variety of offences including rioting and assaulting police.
Earlier, a letter bomb was intercepted at the North’s main postal sorting office.
In one case, a 19-year-old man was stabbed in the back around 1.20am in North Belfast. He was taken to a nearby hospital and police described his condition as stable.
Two men left the area in a silver Renault Clio towards the Antrim Road area and police enquiries are continuing.
Another, a 21-year-old, received non-life threatening injuries when he was stabbed at around 2.20am in the Montrose Street area of east Belfast.
Separately, police are treating a sectarian attack on an Orange Hall in Co Antrim as a hate crime.
Republican and sectarian graffiti was painted on the hall at Coleraine Road, Ballycastle, on the north coast.
Police Service of Northern Ireland (PSNI) assistant chief constable Will Kerr said: “I am pleased that last night was one of the most peaceful in recent years and am encouraged by the responsible behaviour of the vast majority of people involved.
“I appreciate the efforts of all those involved in ensuring this was the case and I would continue to encourage everyone to work together to ensure that today passes off peacefully and that local communities are not disrupted with the violence witnessed in previous years.”
The Northern Ireland Fire & Rescue Service (NIFRS) received 58 bonfire-related calls overnight, 28 requiring intervention by crews.
With the total bill for policing parades and flags disputes in Northern Ireland over the last 20 months standing at around £55m, there is a significant effort to avoid further trouble this year.
In recent years when an Orange Order parade was permitted to pass the Ardoyne, republicans engaged in serious rioting. When it was restricted last year, loyalists were responsible for the disorder.
Almost 700 people were charged or reported to prosecutors in Northern Ireland last year in relation to parade and protest-related disorder.
While not all cases have progressed through the criminal justice system, 561 people have been convicted to date and many have ended up in prison, with five years the stiffest term handed down.