Police officers have reported coming under gunfire as fresh loyalist violence erupted in Northern Ireland over the flying of the Union Flag.

One man, aged 38, has been arrested on suspicion of attempted murder, while two others were also detained amid ongoing street disturbances.

More than 1,000 demonstrators marched on Belfast's City Hall on Saturday, but despite tense scenes and some scuffles the rally passed off without major incident.

There was a heavy police presence, including officers in riot gear with dogs stationed within the historic civic building itself and on surrounding side streets.

But as the flag-waving crowds dispersed, ugly scenes flared again, for the third night in a row, on the Newtownards Road in the traditionally unionist east of the city.

Police again came under attack from a missile-throwing mob of around 100 loyalists, who hurled bricks and fireworks at officers.

A section of the usually busy Newtownards Road, between Bridgend and Hollywood Arches, was shut down because of the sporadic disorder.

There were no immediate reports of any police injuries.

A PSNI spokesman said they were investigating reports from their own officers that a number of shots were fired at police lines.

Conall McDevitt, policing spokesman for the nationalist SDLP, said the firing of shots at police officers ended any claim to legitimacy by protest organisers.

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

"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."