Fresh trouble flared in east Belfast just hours after senior police and politicians on all sides called for peace on the streets.
Officers were attacked again on Monday evening in the lower Newtownards Road area after a series of small demonstrations by loyalists in protest against the decision to restrict the flying of the Union flag above City Hall.
Policing the riots has already cost more than £7 million
A number of roads were blocked for a time. Some motorists held up in long tailbacks complained that police failed to take tougher action to clear masked demonstrators waving flags.
Bus services in the east of the city were also suspended after what Translink described as "two incidents." Water cannons were called in after mobs attacked officers with stones, bottles and missiles. There were no early reports of injuries.
Earlier senior police and politicians united in their demands for an end to the violent protests which have blighted Northern Ireland over the past six weeks. The first minister, Peter Robinson, branded rioters the enemies of democracy and claimed they were being exploited by elements seeking to wreck the peace process.
"You do not respect a Union flag if you are using it as a weapon to charge against someone," Mr Robinson said. "You are not showing respect for the Union flag if you need to wear a mask when carrying it.
"For many the issue of the flying of the Union flag at Belfast City Council is now a cynical cover for the real political agenda which is to destroy the political process."
Northern Ireland minister Theresa Villiers had talks in Belfast on Monday
Civil unrest has erupted in parts of Northern Ireland since Belfast City councillors voted on 3 December to restrict the number of days the Union flag would be flown over City Hall.
To date 101 police officers have been injured, one of whom is still in hospital.
There have been 112 arrests and 85 people, including a number of children, have been charged with public order offences.
The bill for policing the riots has already exceeded £7 million.
Northern Ireland's top police officer Matt Baggott has called for politicians to act quickly to resolve the crisis.
The Police Service of Northern Ireland (PSNI) Chief Constable revealed his commanders on the ground were revising their tactics, but said sweeping protesters off the streets was not a realistic option.
He said: "Even when the PSNI was 12,000 strong it would not have been possible to take such a rigid approach towards protests. Our approach has always been to be measured and responsible.
"We have simply to put public safety first."
Loyalists threw petrol bombs at police and also at homes and a Catholic church in the neighbouring Catholic Short Strand area.
Conall McDevitt, an SDLP member of the Northern Ireland Assembly, and one of the Belfast councillors who voted for the flag to come down, said the attack on St Matthews Church and surrounding houses was a shameful act of hate. He also said the continuing attacks on police were "sick".