BELFAST, Northern Ireland (CNN) -- A policewoman narrowly escaped injury when a petrol bomb was thrown at a police car in Belfast, police said, as tensions in Northern Ireland prompted by a vote on the flying of the Union flag continue to simmer.

At the time of the attack, the car was stationed outside the office of Alliance Party lawmaker Naomi Long, who received a death threat last week. The Police Service of Northern Ireland is treating the incident as an attempted murder.

Long, the Alliance Party's sole lawmaker in the UK Parliament at Westminster, has called on British Prime Minister David Cameron to intervene.

The violent outbreaks were prompted by a decision on Monday of last week by Belfast city councilors to stop flying the Union flag year-round, restricting it instead to certain days.

Northern Ireland First Minister Peter Robinson condemned the attack, saying: "The attempted murder of a police officer in East Belfast was a despicable act of terror.

"The masked men responsible do not act in the name of our Union flag. They are bringing shame on it. My prayers are with the police officers at the center of this attack."

Robinson, of the Democratic Unionist Party, said he defended the right to peaceful protest, but "those intent on violence should stay at home."

About 32 police officers were injured in the past week's violence, Assistant Chief Constable George Hamilton said. There have been 38 arrests in connection with the loyalist disorder.

"It is completely unacceptable that officers who were carrying out their professional duty on behalf of the community should be subjected to a potentially murderous attack," Hamilton said of the petrol bomb attack. "This was a planned attempt to kill a police officer which also put the lives of the public in danger, and it is fortunate there were no injuries."

Clashes also broke out between groups of nationalist and loyalist youths in east Belfast, police said.

Addressing Parliament, Secretary of State for Northern Ireland Theresa Villiers condemned the violence and appealed for calm.

"There can be absolutely no excuse or justification for this kind of thuggish and lawless behavior," she said.

"Nobody can be in any doubt about the government's support for the union and its flag. But those people engaged in the kind of violence we have seen in the past few days are not defending the Union flag. They are dishonoring and shaming the flag of our country."

A number of properties linked to the cross-community Alliance Party, which backed the decision to restrict the flying of the Union flag, have been targeted in the week since the vote.

Alliance Party councilor Linda Cleland said the windows of her car were smashed and several windows in her home broken over the weekend. "This violence must stop," she said. "There is no justification for the attack on my home or the homes and offices of my colleagues."

U.S. Secretary of State Hillary Clinton joined Robinson and Deputy First Minister Martin McGuinness last week in condemning the threat to Long and the outbreaks of violence.

Robinson and Mike Nesbitt, the Ulster Unionist leader, met Monday to discuss political proposals to address widespread concerns across the community, and agreed to hold further talks Tuesday.

Police said Saturday that loyalist paramilitaries were behind some of the violence in Belfast and elsewhere.

The vote on the Union flag followed a summer of heightened tensions between Northern Ireland's Catholic and Protestant communities. Riots in September left dozens of police officers injured.

Just more than a month ago, a prison officer was killed in a suspected dissident Irish Republican Army attack, the first such attack in years. In recent days, a number of suspected dissident IRA members have been arrested.

The recent disorder follows more than a decade during which Northern Ireland has made steady progress toward lasting peace and stability.

The majority of the island 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 unionists, 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 effectively ended the conflict, distrust remains between Catholics and Protestants.

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