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NEW: Unionist leaders say a forum to discuss community concerns will meet Thursday
Police and their vehicles are attacked in a 5th night of violence in East Belfast
The Belfast City Council meets for the first time since its controversial flag ruling
Authorities accuse a loyalist extremist group of ''orchestrating violence''
Pro-British political groups planned to meet this week as part of an effort to defuse tensions and stem some of the worst violence in Northern Ireland in recent memory.
Rioting flared for a fifth-straight night in East Belfast on Monday as protestors attacked police with firebombs, hatchets and sledge hammers.
Authorities accused loyalist extremists of exploiting a decision last month by Belfast officials to stop a century old tradition of flying the Union Jack over City Hall year round.
The leaders of the two main unionist political parties said on Tuesday they would hold a “Unionist Forum” on Thursday at Stormont to address underlying grievances peacefully.
The forum seeks “to engage with the entire unionist community and to address issues of concern. It will seek to channel unionist efforts through political means,” said First Minister Peter Robinson, of the Democratic Unionist Party, and Mike Nesbitt, of the Ulster Unionist Party.
It was not clear if representatives for the protesters would attend.
The British flag has long been a flashpoint between British loyalists – primarily Protestants who want to remain part of the United Kingdom, and Irish nationalists calling for Northern Ireland to join Ireland.
The City Council vote followed a summer of heightened tensions between Northern Ireland’s Catholic and Protestant communities. Riots in September left dozens of police injured.
About 400 people gathered at Belfast City Hall on Monday as the council met for the first time since voting in December to fly the British flag only on certain days, police said.
Demonstrators called for the decision to be reversed. The event was mostly peaceful and was organized via social media, authorities said.
The scene was very different in East Belfast. About 250 people targeted police with gasoline and paint bombs, fireworks and heavy masonry.
Police fired plastic bullets and water cannon in response.
Three police officers were injured, the Police Service of Northern Ireland said. Several people were arrested at the scene of the worst violence.
Clashes also erupted between pro-British and pro-Irish groups at a point where predominantly Protestant and Catholic communities meet.
Authorities said more than 50 officers have been hurt during the protests over the past week.
Read more: Fresh protests break out in Northern Ireland after night of violence
The chief constable for the Police Service of Northern Island blamed the violence on members of the loyalist Ulster Volunteer Force, who were “orchestrating violence for their own selfish motives.”
Northern Ireland’s political leaders have called for an end to the protests and politicians, clergy and community met Sunday to discuss possible ways to achieve that aim.
Read more: Policewoman targeted as Northern Ireland tensions rise
“Everyone involved needs to step back. The lack of control is very worrying,” Chief Constable Matt Baggott told CNN. “The only answer is a political solution.”
Numerous police have been pulled away from normal duties to deal with the demonstrations, Baggott said.
Read more: Police: Loyalist paramilitaries behind Northern Ireland violence
The majority of Ireland gained independence in 1921 following two years of conflict. But six of the nine counties of the province of Ulster chose to stay in the United Kingdom, eventually becoming the country of Northern Ireland.
In the late 1960s, the conflict between mainly Protestant loyalists, who want Northern Ireland to remain part of the United Kingdom, and largely Roman Catholic nationalists, who want it to be reunited with the rest of Ireland, exploded into a political and sectarian war, known as “the Troubles.”
The three decades of ensuing violence between loyalists and the IRA claimed more than 3,000 lives, most of them north of the border. While the Good Friday Agreement of 1998, also known as the Belfast Agreement, effectively ended the conflict, distrust remains between Catholics and Protestants.
Under the terms of the accord, groups on both sides dumped their weapons, and members of Sinn Fein, the political affiliate of the IRA, now work with pro-British politicians in Northern Ireland’s power-sharing government.
Read more: Clinton urges calm amid tensions in Northern Ireland
CNN’s Laura Smith-Spark and Chelsea J. Carter contributed to this report.