BELFAST, Northern Ireland - Northern Ireland police have been using water cannons to fend off brick-hurling protesters in Belfast today as violent demonstrations over flying the British flag stretch into a third straight day.

The Police Service of Northern Ireland says it's investigating reports that a number of shots were fired at police lines.

They say a 38-year-man has been arrested on suspicion of attempted murder.

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

The rally passed largely without incident, but police later came under attack from a mob of more than 100 people hurling bricks and fireworks.

Two men were arrested.

Protesters have been out in force since a Dec. 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.

Today's flare-up followed a tense night in Belfast when nine police officers were injured and 18 rioters arrested.