Northern Ireland police have used water cannons to fend off brick-hurling protesters in Belfast as violent demonstrations over flying the British flag stretched into a third straight day.

More than 1,000 demonstrators marched on Belfast's city hall on Saturday afternoon amid a heavy police presence.

While the rally passed largely without incident, police then came under attack from a mob hurling bricks and fireworks.

"Police have come under sustained attack from crowds of more than 100 people using fireworks, bricks and other masonry. Water cannon has been deployed and two men have been arrested," a statement from police said.

Protesters have been out in force, with sometimes violent results, since a December 3 decision by Belfast City Council to stop flying the British flag year-round.

Such issues of symbolism frequently inflame sectarian passions in Northern Ireland, where Protestants mainly want to stay in the United Kingdom and Catholics want to unite with the Republic of Ireland.

Many Protestants want the council to reverse its decision about the flag, and dozens of police have been injured in ensuing demonstrations.

'Attempted murder'

A 38-year-old man has been arrested on suspicion of attempted murder, police said on Saturday, after reports of shots fired at officers during protests a day earlier in traditionally pro-British east Belfast.



On Friday night, nine police officers were injured and 18 people were arrested in the second consecutive night of disorder involving up to 300 people hurling petrol bombs, fireworks, ball bearings and masonry.



Conall McDevitt, a member of the Northern Ireland assembly for the republican SDLP, said the use of guns undermined the demonstrators' claim to be involved in legitimate protests.



"Whatever grievance some people may have had, it is totally lost when they allow people to use these protests as cover for attempted murder," he said.



"There is only one response possible, and that's a firm policing response against everyone involved in illegal protests and anyone seeking to organise or encourage illegal or violent demonstrations."



On Friday, First Minister Peter Robinson, the leader of the Protestant, pro-British Democratic Unionist Party, said attacks on police officers were a "disgrace, criminally wrong and cannot be justified".



"Those responsible are doing a grave disservice to the cause they claim to espouse and are playing into the hands of those dissident groups who would seek to exploit every opportunity to further their terror aims," he said.



The December flag vote has raised tensions in the province, which endured three decades of sectarian violence until 1998 peace accords led to a power-sharing government between Protestants and Catholics.