Police came under petrol bomb attack from masked gangs tonight after a high-profile republican was arrested in connection with the murder of two soldiers in the North.
Former IRA prisoner Colin Duffy, 41, has broken away from mainstream republicans and criticised Sinn Féin's decision to back the new Police Service of Northern Ireland (PSNI).
Following his arrest, gangs took to the streets near his home in Lurgan, Co Armagh, and police were pelted with stones before petrol bombs were hurled at PSNI vehicles.
Duffy was one of three men arrested this morning by police probing the murders of Patrick Azimkar, 21, and Mark Quinsey, 23, who were gunned down by the dissident republican Real IRA as they collected pizzas at the gates of Massereene Barracks in Antrim last Saturday night.
A tense stand-off developed in Lurgan tonight, with youths forming makeshift barricades to block the railway lines in the town.
Duffy and two other men, aged 21 and 32, were arrested in police raids this morning in Lurgan and Bellaghy, Co Derry.
All three were being questioned at Antrim police station tonight.
Duffy came to prominence in the 1990s after he was acquitted of the murder of a soldier when it emerged that a key witness against him was a loyalist paramilitary. He was later arrested in connection with the subsequent murder of two police constables, but the case collapsed.
His solicitor, Rosemary Nelson, received threats after representing him in court and she was murdered in a loyalist car bomb attack at her Lurgan home in 1999.
Her death is now the subject of a high-profile public inquiry.
Police teams in forensic suits carried out extensive searches of Duffy's house on a private estate in Lurgan today.
The two soldiers were killed in the Real IRA ambush at their barracks hours before they were to fly to Afghanistan. Two other soldiers and two pizza delivery men were wounded in the attack.
Detectives are examining CCTV footage from the area around the barracks and also what is believed to be the gunmen's getaway car which was found abandoned seven miles from the scene of the murders.
The green Vauxhall Cavalier, registration TDZ 7309, had been bought two weeks earlier.
It is understood the gunmen had tried to burn the car, but it had not ignited.
The claim has led to speculation that the vehicle's discovery may have provided police with opportunities to obtain forensic evidence.
The two young soldiers were the first to be murdered in the North in 12 years. Lance Bombardier Stephen Restorick was killed by an IRA sniper in 1997.
Police are also questioning three people over the murder of Police Constable Stephen Carroll, 48, who was killed by gunmen from the Continuity IRA in an attack launched in Craigavon, Co Armagh, on Monday night.
His funeral yesterday was attended by senior officers, politicians and leaders from across the community.
The Continuity IRA and the Real IRA are dissident republican groups which broke away from mainstream republicanism in opposition to the peace process.
They rejected the decision of the mainstream IRA to end violence, decommission weapons and follow purely peaceful means to pursue republican political goals.
Duffy is a member of the republican protest group Eirigi, which has not supported the new police service, but which insists it is a peaceful pressure group.
He attracted criticism last year when serious rioting in the Lurgan area led to attacks on police, which he failed to condemn.
After police came under gun and petrol-bomb attack during two days of rioting, he said the episodes were a symptom of a section of the nationalist community refusing to accept the PSNI.
But in the wake of the murder of the soldiers in Antrim and of Pc Carroll in the Lurgan/Craigavon area, Duffy and the Eirigi group were challenged to condemn the killings.
Eirigi, which is Irish for "rise up", released a statement in response to the pressure, claiming it did not support violent groups.
Earlier this week it said: "Eirigi is an open, independent, democratic political party which is not aligned to, or supportive of, any armed organisation."
But it added: "While supporting the right of any people to defend themselves from imperial aggression, Eirigi does not believe that the conditions exist at this time for a successful armed struggle against the British occupation.
"As can be seen from the recent attacks on Britain's Armed Forces, it is clear that not all republicans agree on how the British occupation should be resisted at this time.
"Those who carried out those attacks are best placed to explain their own rationale."
The Eirigi group includes Breandan Mac Cionnaith, who was unavailable for comment today, but who came to prominence in the 1990s as the leader of the nationalist Garvaghy Road Residents Coalition which opposed Orange Order parades through the Catholic enclave in Portadown, Co Armagh.
He resigned from Sinn Féin in protest over its decision to back the new police service, but has in the past said Eirigi is a purely political group.
Police searching Duffy's house came under attack today from youths who hurled missiles at officers.
Bricks littered the scene this afternoon as the police searches continued.
The PSNI activity came after politicians from all sides united against the dissident republican murders.
Earlier this week, First Minister and Democratic Unionist Party (DUP) leader Peter Robinson reaffirmed his party's commitment to the power-sharing government at Stormont.
Deputy First Minister Martin McGuinness, of Sinn Féin, branded the killers criminals and traitors who had defied the expressed wishes of the people of Ireland to support the political structures born out of the Good Friday Agreement.
Both political leaders are in the United States and will meet President Barack Obama on Tuesday in Washington as part of St Patrick's Day events.
Today, Ulster Unionist leader Reg Empey said: "It is in no-one's interests to drag Northern Ireland back to the past and it is in no-one's interests that fear and instability become the hallmarks by which the rest of the world recognises us."