DUBLIN, Ireland - Northern Ireland leaders appealed for calm Thursday after Protestant militants attacked offices and a home connected to the most compromise-minded political party over its support for reducing the display of British flags on government buildings.

The overnight violence in two Belfast suburbs came on the eve of Secretary of State Hillary Rodham Clinton's planned visit Friday to the capital of the British territory. It underscored how divided Northern Ireland remains despite the broad success of a peace process that has stopped paramilitary violence but done little to bring down barriers between rival British Protestant and Irish Catholic communities.

"I'm looking forward to my visit to Belfast tomorrow to see for myself what the situation is," Clinton said at a Dublin news conference alongside Irish Prime Minister Enda Kenny.

Protestant hard-liners have responded violently to a vote Monday in the Belfast City Council to reduce sharply the flying of the British flag atop the city hall. The Alliance Party, which represents middle-ground opinion and seeks support from both sides, holds the balance of power on the council. Alliance voted with the Catholic side to take down the flag except for 18 official days annually; the Protestants had wanted it to stay up 365 days a year.

Several hundred Protestant protesters broke through the city hall's gates Monday night and injured 15 police officers. Associated Press photographer Peter Morrison suffered serious head and hand wounds during the melee, during which he says police beat him with clubs.

On Wednesday night more than 1,500 Protestants rallied in the northern suburb of Carrickfergus demanding that the British flag be restored atop Belfast's municipal headquarters. The protest soon descended into attacks on riot police. Four officers were injured and responded with volleys of British-style plastic bullets, flat-nosed cylinders designed to knock down rioters with punishing blows. They also arrested four suspected rioters.

Some in the crowd set fire to the nearby Carrickfergus office of Alliance, destroying it. And to the east of Belfast, vandals poured gasoline on the locked front of another Alliance office in Bangor, but police said a passing patrol spotted the attackers and forced them to flee before they could light a fire.

Also in Bangor, the front window of a couple who are both Alliance politicians was vandalized just after midnight Thursday, and the couple said they now were afraid to stay in their home with their 17-month-old daughter.

"Our daughter could have potentially lost her life. Is a flag worth this, seriously?" Michael Bower told the BBC as he sat on his sofa with his wife, Christine, beside him and their child on his lap.