A man was stabbed in the back in Co Down and 18 people were arrested for public disorder in the student area of Belfast following St Patrick's Day.
The stabbing took place outside a bar in Market Street, Downpatrick, during late-night disturbances. The man's injuries are not thought to be life-threatening.
It was one of a number of violent incidents across the North, with the PSNI intervening in street disturbances in Derry; Maghera, Co Derry; and Ballymena, Co Antrim.
In Derry, seven people were arrested for a range of public order offences including possession of an offensive weapon. A teenage girl was injured in the face by a bottle and a PSNI officer assisting her was also injured.
Fighting was reported in Ballymena and cars were damaged in street violence. Police officers were attacked by stone throwers when they intervened.
In Maghera, a large-scale fight broke out in the town and police were again attacked when they moved to break up the crowd.
In the Holy Land area of south Belfast, there was protracted unrest involving students from a number of colleges and the two main universities. Police arrested 18 people and reported others to university authorities so that disciplinary action could be taken. The disturbances were condemned by the Deputy Chief Constable, Paul Leighton.
Residents have again complained about the rowdy behaviour of students and both Queen's University and the University of Ulster are operating disciplinary mechanisms following a spate of similar incidents last year.
Prof Gerry McCormack, who is in charge of student discipline at Queen's University, said he was "disappointed" that appeals for responsible behaviour by students had "fallen on deaf ears".
"There are certainly some of the activities on the street that would attract fines or even suspensions when people appear before the disciplinary committee," he warned. - Dan Keenan