Reuters

Loyalists clash with police officers outside the City Hall in Belfast following a vote by local councilors to stop flying the British flag every day.

Fifteen police officers were injured when hundreds of people tried to storm Belfast City Hall in Northern Ireland over a plan to stop flying the British flag as it currently does every day of the year, ITV News reported.

The violence broke out after Irish nationalist councilors from the Sinn Fein and SDLP parties voted to take down the flag which has flown above the city hall every day since the building was opened in 1906.

The decision means the flag will be flown only for 17 days of the year, as is the case at the provincial assembly at Stormont.

Nationalist and Unionist parties share power under a 1998 peace deal that largely ended 30 years of sectarian violence in which more than 3,600 people died.

Read more on this story from ITV News

Many of the protesters who clashed with police were carrying British Union flags.

Reuters reported that the attempt to storm the building was repelled by police.

A photographer from the Press Association news agency and two security guards were also injured, a police spokeswoman told Reuters.

Peter Morrison / AP

Police and protesters face off during clashes that saw 15 officers and three others injured.

Dozens of police hurt in Northern Ireland sectarian clashes

Democratic Unionist Party councilor Ruth Patterson described the vote to remove the flag as "divisive, destructive and disrespectful of anything remotely Protestant, anything remotely British," ITV News reported.

Northern Ireland's First Minister Peter Robinson condemned the violence.

"There is no excuse or justification for attacks on police officers, council staff, and property," he said, according to ITV News.

"Such behavior is not representative of those who campaigned to maintain the Union flag flying over Belfast City Hall," he added. "Those who talk most about building community relations have by their actions in the council substantially damaged relations across the city."

Queen Elizabeth to hold historic meeting with former IRA commander

Nationalist parties, which aspire to break from the U.K. and join a united Ireland, last year for the first time secured more seats on the council than Unionist parties, which support maintaining Northern Ireland's position in the United Kingdom.

Gerry Kelly, a member of the Northern Irish Assembly, strongly criticized the police, according to ITV News.

"I have to say, and I don't use these words unless I really mean them, it was a disgraceful police operation -- or lack of a police operation," he said. "If that had been 1,000 or more republicans, it would have been very different."

Ireland PM in historic tribute to veterans on British Remembrance Day

"They indiscriminately attacked cars. We are very, very lucky that they didn't get into the building or we could have been dealing with a lot more injuries," he added. "I am angry because it's not as if they were taken by surprise. This was a well-planned protest."

ITV News, a U.K. partner of NBC News, and Reuters contributed to this report.

More world stories from NBC News:

• Supporters of Islamist president push Egypt to tipping point
• North Korea pays tribute to Kim Jong Il's 'threadbare' parka
• ANALYSIS: Egyptians warn Morsi is no friend of US
• Bread and expired milk: School lunch scandal sparks outrage in China
• PhotoBlog: Building South Sudan from scratch
• ANALYSIS: UN Palestinian vote a personal victory for Abbas
• Fast cars go cheap as bubble bursts in 'China's Dubai'
• Experts: Antarctica, Greenland ice melting into sea

Follow World News from NBCNews.com on Twitter and Facebook