Politicians and church leaders in Northern Ireland held talks on Sunday in a bid to stop the violence over the flying of the British flag.

After three nights of rioting and attacks on police, Northern Ireland's chief police officer Matt Baggott said 52 officers had been injured, but he warned his force would deal firmly with the violence for as long as it was necessary.

"You may be assured there will be sufficient resources in the event of more disorder for however long is necessary," said Baggott, the PSNI chief constable.

Police used water cannon and fired baton rounds in Belfast on Saturday as they confronted more than 100 loyalist protesters who were throwing fireworks and bricks.

Officers reported coming under gunfire. A 38-year-old man was arrested on suspicion of attempted murder.

The discussions aimed at ending the violence took place at a Belfast church, but Robin Newton, of the Democratic Unionist Party, said a lack of engagement from protest organisers was making it difficult to see an end to the unrest.

"We have to find a way out of this, but how we do it I don't know," he admitted.

The rioting on Saturday followed a largely peaceful demonstration by more than 1,000 people outside Belfast city hall against the city council's decision last month to limit the days it flies the British flag, or Union flag, each year.

The ruling on December 3 was viewed by pro-British loyalist groups as a concession too far to republicans who want Northern Ireland to be part of Ireland.

Protesters immediately took to the streets and there have been on-off demonstrations in Belfast ever since.

So far, 70 people have been arrested in connection with the sporadic rioting and 47 people have been charged with criminal offences.

Terry Spence, chairman of the Police Federation for Northern Ireland, which represents the interests of police officers, said the firing of shots at police proved that paramilitaries had infiltrated the protests.

"What it quite clearly demonstrates is the fact that paramilitaries have hijacked this flags protest issue and they have now turned their guns on the police," he said.

"There is no doubt that it has been exploited by the paramilitary grouping known as the Ulster Volunteer Force, and it is very clear that there are members of the UVF, leading members of the UVF, who are exploiting this and are organising and orchestrating this violence against police officers," he said.

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