Trouble flares at flag protests in Belfast
Trouble broke out in Belfast and other towns on Monday night as loyalists again protested against restrictions on flying the union flag on the city hall.
Police came under attack in Newtownards Road, where 200 loyalists congregated.
One officer was injured in Sandy Row, near the city centre, when paint bombs, fireworks and bricks were thrown.
South Belfast, Lisburn, Carrickfergus and Portadown also saw trouble. Police said they had arrested 15 people in total, including an 11-year-old child.
The latest trouble comes after more than two weeks of demonstrations by loyalists over the decision by Belfast City Council to stop flying the union flag every day.
BBC Ireland correspondent Mark Simpson says the latest violence was "low level" but happened in a wide range of areas. He says a 12-year-old and two 13-year-olds were also among those arrested.
Political leaders at Stormont have made repeated calls for the violence to stop but the protesters are simply ignoring them, our correspondent says.'Totally unacceptable'
The PSNI said about 80 protests took place across the province on Monday, with numbers ranging from small groups to hundreds of people. They have appealed for an end to the violence.
Assistant Chief Constable Dave Jones said: "While most of the protests were peaceful, the violence witnessed in some areas tonight is totally unacceptable.
What started as a political problem in Belfast quickly became a security headache and is now fast becoming an economic nightmare.
Two weeks of flag protests and roadblocks in the city have seen visitor and shopper numbers fall at what is supposed to be the busiest time of the year.
Some pubs estimate a 20% drop in festive business.
Christmas Day is only a week away but there is no end in sight to the flag protests.
It is not just a problem for the police and politicians but the economic well-being of the city - and its reputation.
"This is now the third week of protests and I am appealing to everyone involved to take a step back from this. It cannot and should not continue."
In Portadown, a man was taken to hospital after being injured in a road accident during a protest.
In south Belfast, protesters set fire to bins and placed them across the Donegall Road near the City Hospital.
In Gaol Square, Armagh city, police arrested a 19-year-old man after a firework was thrown at police from a crowd of protesters.
Following a protest at Carrickfergus, about 11 miles from Belfast, protesters entered the town hall, disrupted a meeting and threatened councillors. No-one was injured.
Police dispersed the crowd and people were able to leave the building.
Alliance Party Councillor Noel Williams said that about five protesters infiltrated a meeting of Carrickfergus Borough Council "and carried out a full frontal attack on democracy".
He said councillors were subjected to verbal abuse by about five protesters who banged on desks and chairs.
"It is unacceptable that the town hall was not under police surveillance, especially as violence has broken out at previous protests," he said.
"People have a right to protest peacefully, but this incident tonight put many people's safety at risk and must not be tolerated."
In Lisburn, County Antrim, a crowd blocked Longstone Street. Police have asked people to avoid the area.
At Shaw's Bridge, in south Belfast, police diverted traffic as youths attempted to hijack vehicles. The road has now been re-opened.
Protests also took place in Londonderry and Ballyclare.
The protests, initially timed to coincide with the rush hour, were also held in several areas of Belfast including the Albertbridge Road, Newtownards Road and Limestone Road.
About 50 loyalists blocked traffic at Glendermott Road in Londonderry.
A similar number disrupted traffic at the junction of Tates Avenue and Boucher Road in Belfast.
Earlier on Monday, the leaders of the DUP and UUP, Peter Robinson and Mike Nesbitt, appealed to loyalists to call off the protests.Impassable
Police closed the M2 Fortwilliam off-slip to the Shore Road because of a protest at Mount Vernon.
In south Belfast, the Ormeau Road re-opened after being blocked for a period
The Upper Malone Road at the House of Sport has also re-opened following a protest at the Dub.
In the north of the city, the Limestone Road was blocked at York Street and the Crumlin Road at Hesketh Park.
In Londonderry, drivers were advised to avoid the Glendermott Road into the city and the Rossdowney Road.
Ballyclare town centre, Coleraine and Broughshane village were also blocked by protesters.