US Secretary of State Hillary Clinton has called for an end to a new outbreak of violence in Northern Ireland and urged all parties to confront the sectarian challenges together.
Mrs Clinton has made a nostalgic return to Belfast but with tension running high over flags, the peace that she and her husband, ex-president Bill Clinton, helped to build remains far from perfect.
The unrest erupted on Monday night after the city council voted to only fly the Union flag over City Hall on designated days during the year. The Union flag had flown over the building every day for over 100 years until the vote.
A loyalist protest outside the council meeting turned violent and 15 police officers were injured as well as two security guards and a press photographer.
Another protest in Carrickfergus on Wednesday also left four police officers injured. And there were minor disturbances in Ballymena on Thursday night.
Sky's Vicki Hawthorne said: "Members of the neutral Alliance Party have also been targeted during the disorder because of their stance during the flag vote. The home of two councillors was paint bombed and the office of an MLA was destroyed.
"The Alliance Party MP for East Belfast Naomi Long has received a death threat which has been linked to the flag protests."
Mrs Clinton, who has already visited Dublin, was speaking at Stormont, where she met First Minister Peter Robinson and Deputy First Minister Martin McGuinness before attending a lunch at Titanic Belfast in the city's docklands.
She said: "Peace does take sacrifice, compromise and vigilance day after day. We've seen that again this week that the work is not complete. We have seen violence break out again.
"I join with both Peter and Martin and all the leaders and citizens who have condemned the recent attacks in Belfast and around the whole area.
"All parties need to confront the remaining challenges of sectarian division peacefully and together." She added violence was "never an acceptable response to disagreements".
Mr Robinson has urged loyalists to suspend their protests over the flag issue. "Those who riot and engage in violence do a disservice to the flag they claim to represent," he said.
This is Mrs Clinton's second visit as secretary of state. The last was in 2009 when she encouraged the devolution of policing and justice powers from London to Belfast.
She arrived in Northern Ireland just hours after a bomb was discovered in a car. Officers investigating dissident republican activity had stopped the vehicle in the Creggan area of Londonderry on Thursday evening.
Two men aged 47 and 49 were arrested at the scene at about 8.40pm. Two others, also in their 40s, were detained later.
Security chiefs believe dissident republicans opposed to the peace process were planning an attack in the centre of the city, next year's UK City of Culture.
Police have also revealed the discovery of a letter bomb at a postbox in a loyalist area of Co Down. The bomb was made safe and taken away for forensic examination.
It was 1995 when the Clintons paid their first historic visit to Northern Ireland. Thousands turned out to greet them and to herald the dawn of the peace process.
Teenager Sharon Haughey, who had written a letter about 'The Troubles' to the White House, welcomed them to Armagh. She's now the city's Lord Mayor and gives them the credit.
"The Clintons have played a very important role in the pathway that I have chosen in my life," she said. "They gave me a platform as a very ordinary 14-year-old schoolgirl.
"They gave me an extraordinary opportunity and I decided to use that opportunity to help shape that future that I wanted and that's really why I'm here today."