Detectives are today questioning nine people in connection with the murders of two soldiers and a police officer in the North after a series of raids where investigators seized a gun and ammunition.
The weapons seizure was made in Craigavon, Co Armagh, last night by officers probing the policeman's murder.
This came as officers who arrested high-profile republican Colin Duffy in Lurgan over the murder of the two soldiers were attacked by masked youths.
The murders were carried out by the Continuity IRA and the Real IRA dissident republican groups, who are intent on derailing the peace process, and who reject the decision of the mainstream IRA to end violence, decommission weapons and follow purely peaceful means to pursue republican political goals.
Detectives are now questioning five people in connection with the murder of Police Constable Stephen Carroll, 48, who was killed by gunmen from the Continuity IRA in an attack launched in Craigavon on Monday night.
Among them is a 30-year-old woman and a 37-year-old man arrested last night in the Craigavon area.
A further three men were yesterday arrested by police probing the murders of soldiers Mark Quinsey, 23, from Birmingham, and Patrick Azimkar, 21, from London, who were gunned down by the Real IRA as they collected pizzas at the gates of the Massereene Barracks in Antrim last Saturday night.
Detectives investigating the attack, where two soldiers and two pizza delivery men were also injured, last night arrested a further man in Antrim.
Duffy was one of the three men arrested yesterday morning by police probing the murders of the soldiers.
The well known republican and the two other men, aged 21 and 32, were arrested in police raids in Lurgan and in Bellaghy, Co Derry.
All three were being questioned at Antrim police station last night.
The 41-year-old former IRA prisoner 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 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 over 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 later 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 probing allegations of security force involvement in her killing and today marks the 10th anniversary of her murder.
Police teams in forensic suits carried out extensive searches of Duffy's house on a private estate in Lurgan yesterday.
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.
Last night police revisited the scene of the attack and repeated their appeal for information on the vehicle, while they also asked for anyone who saw anything suspicious in the area to come forward.
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.
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.