Police had no intelligence to suggest there would be violence at a flag protest in Belfast, the officer leading the operation has admitted.

Rioting loyalists injured 15 PSNI members, two council security guards and a press photographer when they tried to smash their way into Belfast City Hall after a controversial vote on the Union flag.

Chief Superintendent Alan McCrum said: "A diverse crowd, of up to 1,500 at the peak of the protest, consisting of men, women, young people, mothers with children in buggies and wheelchair users, gathered at the back of City Hall.

"Police had no definitive intelligence to suggest that there would be any violence and given the diversity of the people protesting, the operation had to be managed very carefully."

On Tuesday morning the Union flag was removed from City Hall for the first time in more than a century. The move brings the building into line with Stormont's Parliament Buildings where it only is flown on designated days.

Police were pelted with missiles including fireworks, bricks, bottles and stones. A number of protesters also brought bolt cutters to break a lock on the iron gates of City Hall and at one point a masked mob tried to kick down the back door of the building.

Politicians and community workers across Belfast have claimed the violence was orchestrated through social networking sites such as Facebook and Twitter.

Sinn Fein Policing Board member Gerry Kelly, who was inside City Hall at the time of the riot, described the policing operation as inadequate. He claimed officers were over-run and ill-equipped when the protest turned ugly.

Policing Board Chairman Brian Rea also raised questions about the preparedness of the PSNI ahead of the protest.

Mr McCrum defended his decision to deploy community beat officers and not the riot squad to monitor the volatile situation. "This disorder was completely disgraceful," he added. "People have the right to lawful protest, but democracy has a right to be protected."