Police car petrol-bombed opposite MP Naomi Long's office
The Ulster Unionist leader has called for an end to loyalist street protests after loyalists threw a petrol bomb into a car as a policewoman sat inside.
Police are treating the attack close to Alliance Party MP Naomi Long's east Belfast office as attempted murder.
A gang of six men smashed the car's back window and threw in the bomb at about 19:35 GMT on Monday. The woman escaped unhurt.
The violence is to be raised in the House of Commons later on Tuesday.
It followed loyalist protests about last week's decision by Belfast City Council to fly the union flag at city hall only on certain days, instead of all year round.
In the past week, as trouble flared across Northern Ireland, 29 police officers were injured and 38 people have been arrested.
Ulster Unionist leader Mike Nesbitt said on Tuesday that violence associated with protests could not be tolerated.
"It is anti-British to attack
Ms Long, the MP for East Belfast, received a death threat last week. A police car has been stationed outside her Newtownards Road office since then.
Condemning Monday night's attack, Ms Long said: "There is no doubt in my mind that the car was targeted because it was undertaking patrols in the vicinity of my office and I find that absolutely repugnant."
She said recent attacks on the Alliance Party bore "all the hallmarks of a pogrom".
Assistant Chief Constable George Hamilton said: "This was a planned attempt to kill a police officer which also put the lives of the public in danger and it is fortunate there were no injuries as a result of this attack.
"I am urgently appealing to those involved in ongoing protests to listen to their political leaders and step back from protest activity before someone is seriously injured or killed."
Northern Ireland Secretary Theresa Villiers said MPs would be given the opportunity to air their views on the violence in Parliament later on Tuesday. She said it was "totally unacceptable".
"It is incredibly important that those involved listen to the political leadership," she said.
Labour's shadow Northern Ireland secretary Vernon Coaker said the government needed to act.Barricades
There was also rioting in the loyalist Village area of south Belfast on Monday night.
Police were attacked with petrol bombs, bricks, masonry, bottles and fireworks, and attempts were made to put burning barricades across roads.
Police responded with water cannon.
At the Short Strand/Castlereagh Street junction in east Belfast, riot police separated rival crowds throwing missiles, although a small crowd of nationalist youths continued to stone police Land Rovers for a period.
Police are also investigating reports of an attack on a bar in Thomas Street, Armagh, which is owned by the husband of a Sinn Fein councillor.
It was reported that at about 21:00 GMT, windows in the bar were smashed and fireworks thrown inside. There were no reports of any injuries.
Publican Bernard Rafferty said a loyalist protest march had been passing the bar at the time of the attack.
"I was serving behind the bar and I noticed a crowd came by the window with union jacks - within 10 seconds I head the windows starting to go in," he said.
"Next minute the door was bust open and there were large, what I thought at the time were pipe bombs, but they were large rockets fired into the bar."
At about 21:50 GMT, a car struck three men on the Newry Road in Armagh before being driven away. There was a loyalist protest in the area at the time.
The men's injuries are not thought to be life-threatening. A 17-year-old boy was arrested a short time later in the Cavanacaw Road area.
Alliance Party members and premises have been targeted since last Monday's vote on the city hall flag.
Alliance, Sinn Fein and SDLP councillors voted to limit the flying of the flag while the Democratic Unionist Party (DUP) and Ulster Unionists (UUP) opposed the move.
Rush-hour traffic was also disrupted in Belfast on Monday by a series of protests.
Some motorists moved less than a mile in the space of an hour.
Police maintained a presence at a number of locations in the city as roads were blocked by crowds carrying union flags and banners.
They said the biggest protest had been in Dundonald on Belfast's eastern outskirts, where about 500 people took part.
Monday was the eighth consecutive night on which loyalists have held demonstrations.
There have also been protests in towns such as Ballyclare, Limavady and Lisburn. But there was no violence.
The Roads Service said salting operations in the Ballyclare area had been affected by protests and as a result some roads have not been treated.'Bringing shame'
Meanwhile, First Minister and DUP leader Peter Robinson and Mike Nesbitt, the Ulster Unionist leader met on Monday night to discuss the flags issue.
In a statement they said they had "agreed to work on a joint basis with a view to urgently bringing forward political proposals to address widespread concerns across the community.
"Further discussions will take place tomorrow in order to finalise a strategy."
Both men condemned Monday night's attack on the police in east Belfast.
"The attempted murder of a police officer in east Belfast was a despicable act of terror," the first minister said.
"The masked men responsible do not act in the name of our union flag. They are bringing shame on it."
Mr Nesbitt said: "It was a cowardly act by a masked gang. There is nothing British about attacking police officers or blocking the entrance to an acute hospital to prevent ambulances getting in and out."
Meanwhile, the DUP is proposing a process of consultation on increasing the number of days the union flag is flown over Parliament Buildings at Stormont.
The proposal is due to be put forward by DUP MLA Peter Weir at Tuesday's meeting of the assembly commission - the cross-party group that manages the estate.
The flag currently flies over the building for 15 days a year.