US secretary of state Hillary Clinton urged protesting loyalists to end street violence today amid heightening fears of further trouble at demonstrations against a decision to restrict the flying of the Union flag at Belfast City Hall.
A death threat against the east Belfast MP Naomi Long marked a serious escalation in tensions after arson attacks on offices used by her non-sectarian Alliance Party.
Even though Unionist Party leaders, including the Northern Ireland First Minister Peter Robinson called for a suspension of planned protests until the new year, security chiefs are gearing up for sporadic outbreaks of new violence, especially in the greater Belfast area.
Loyalists have targeted the Alliance Party after blaming them for backing the nationalist SDLP and Sinn Fein to push through a vote to limit the flying of the flag to designated only days.
Mrs Clinton who met with Mr Robinson and the deputy First Minister Martin McGuinness at Stormont Castle, Belfast today before returning to American at the end of a brief European tour, said the threat on Ms Long's life was absolutely unacceptable.
Mrs Clinton said: "There will always be disagreement in democratic societies, but violence is never an acceptable response to those disagreements. All parties need to confront the remaining challenge of sectarian divisions, peacefully together."
With loyalists threatening another protest in Belfast tomorrow - expected to be the busiest shopping day so far this year - Mrs Clinton said: "People have strong feelings, but you must not use violence as a means of expressing those strong feelings.
"The only path forward is a peaceful democratic one. There can be no place in the new Northern Ireland for any violence. The remnants of the past need to be quickly, unequivocally condemned. Democracy requires dialogue, compromise and constant commitment by everyone to protect the rights of everyone."
Alliance Party offices in Carrickfergus, Co Antrim and Bangor, Co Down - where a councillor's home was also damaged - have been attacked.
Apart from Belfast, there has been trouble as well in Carrickfergus and Ballymena, Co.Antrim, and although nothing on the level of violence earlier this year in Belfast at the height of the so-called marching season, security chiefs fear there is the potential of it getting worse and more widespread.
There is no evidence of the trouble being orchestrated by paramilitaries. Social networking sites are being used to gather crowds, but even though they have distanced themselves from the protests, condemned the threat on Ms Long's life, and called for restraint, the two main Unionist parties have been accused by Sinn Fein and the nationalist SDLP of whipping up tensions and lacking leadership.
Jim McVeigh, a former IRA leader in the Maze Prison and leader of Sinn Fein inside City Hall has also been warned his life could be in danger.
Ms Long has been advised by the police to stay away from her home and her east Belfast constituency offices for her own safety, met with the US Secretary in a later function at the Titanic Centre. She won the east Belfast seat from Mr Robinson at the last General Election.
Tonight she vowed she would not be intimidated and declared: "This will not prevent me providing a constituency service to the people who elected me."
The protest action mob violence will be discussed at the Northern Ireland Assembly on Monday, but in the meantime the leadership of the two main Unionist parties is under pressure to do everything to calm the situation. The speed and the scale of the trouble which erupted, especially in the run up to Christmas, shocked all sides.
The walls of a Protestant church hall at Glenavy, near Crumlin, Co Antrim on the outskirts of west Belfast, was daubed with graffiti.
Mr Robinson said: "There is no excuse for violence and the riotous behaviour we have witnessed over recent days. Those who riot and engage in violent attacks do a disservice to the flag they claim to represent.
"Such activities must stop immediately and must be condemned without qualification by everyone in the community. This is a time for calm and for people to channel their energies into democratic activities and politics.
"Homes, offices and individuals being attacked far from aiding any cause only damage and detract. Such criminal behaviour also distracts from the real debate."
Mr McGuinness said the death threat was work of fascists who could not accept the democratic decision of Belfast City Council.
He said: "No matter what happens on the streets our institutions, the institutions of the Good Friday Agreement, of the St Andrews Agreement and of the Hillsborough Agreement we are going to stick together. We are going to give support to those police services north and south in their efforts to bring to heel those people who would try and drag us back to the past."
Belfast City Hall is now one of many civic buildings across Northern Ireland, including Parliament Buildings, Stormont, where the flying of the flag is limited to designated dates, like the Queen's Birthday.
Tonight, Mr Robinson who claimed the City Hall vote was divisive and provocative, revealed that his Democratic Unionist Party had submitted a motion in a bid to begin a process to extend the number of days the flag is hoisted at Stormont.
Meanwhile, four men are being questioned tonight after police in Londonderry foiled an attempt by dissident republicans to attack police with an improvised, armour piercing home made rocket - similar to devices used in Afghanistan and Iraq.
Three of the men were detained when a car was stopped and missile found in the city's Creggan estate. A fourth man was arrested nearby.
Officers had mounted a major surveillance operation and believe rocket was going to be used in a close range attack on one of their Land Rovers or patrol cars in the hours before Mrs Clinton's arrival in Belfast.