The PSNI has condemned sporadic disorder which occurred in areas of Belfast, Newtownards and Londonderry.
A number of vehicles were hijacked and torched amid heightened tensions on the Eleventh night.
Police also attended security alerts overnight in Belfast.
Trouble flared for a fifth consecutive night in Londonderry with the Lecky Road fly-over in the Bogside blocked by fire.
Meanwhile, masked men used burning cars to block roads close to the Ulster Hospital in Dundonald on the outskirts of Belfast, while a bus with passengers on board was hijacked before being set alight in nearby Newtownards.
None of the passengers were injured in the incident which took place around 7.30pm on Wednesday
The bus was hijacked in Blenheim Drive and later set on fire.
Police also attended the scene of nearby Messines Road which was blocked by burning tyres.
On the Upper Newtownards Road in Dundonald a number of masked males pushed a car into the road and set it on fire close to Robbs Road at around 9.45pm.
A further report was received that two cars were set on fire close to the nearby Carrowreagh Road.
There were a number of other security alerts in the east of the city through the night.
One forced the closure of the Sydenham by pass dual carriageway, meaning passengers were unable to exit the adjacent Belfast City Airport for a period.
A number of homes had to be evacuated for a time in the Newtownards Road area.
Army bomb experts had to examine a due to a suspect car.
It is believed the vehicle was hijacked earlier this evening in north Belfast.
Police say the road has now reopened and residents have returned to their homes.
A controlled explosion was carried out on a suspicious object on the Ravenhill Avenue. The alert was declared to be a hoax.
Wednesday's incidents unfolded amid a police warning that loyalist paramilitaries were planning to "orchestrate and participate in serious disorder" in east Belfast.
The violence came after loyalists expressed anger at moves to limit the size of bonfires at two controversial sites in the east of the city.
Assistant Chief Constable Alan Todd said: “The general levels of calls for assistance last night were similar to what we have seen in recent years however we did deal with disorder and disruption which seen 13 vehicles burnt out in Belfast and Newtownards and petrol bombs thrown at my officers in Derry/Londonderry. There were also a number of security alerts.
“No part of this is acceptable and today we are looking at the evidential picture to pursue lines of enquiry.
“I would like to pay tribute to the job that my officers, along with other emergency services, did last night.
ACC Todd continued: “I sincerely hope that today passes off peacefully and that the thousands of people who are attending community events and parades can do so enjoyably and safely.
“I would ask all of those with influence to work with us to ensure the safety of all.
“Our priority remains, keeping people safe and I want to reassure people this morning that our response, should there be an further disorder, will continue to be proportionate with the necessary resources in place to detect and deter those responsible."