The Provisional IRA is still recruiting, training, gathering intelligence, engaging in so-called "punishment" attacks and in major organised crime, according to the latest report of the Independent Monitoring Commission (IMC).
All other republican and loyalist paramilitary groupings also remain active, while the Ulster Defence Association (UDA), currently non-proscribed, has been responsible for two murders since September, the IMC said in its fifth report yesterday.
The IMC said IRA members were involved in the murder of Robert McCartney.
"We do not believe that the central PIRA leadership sanctioned it in advance, but those concerned may have believed they were acting at the direction of a local senior PIRA member at the scene," it said.
"After the event there was prompt PIRA intervention to protect its members and to obstruct the investigation, including by cleaning up the scene and by the intimidation of witnesses.
"By their immediate and subsequent interventions, PIRA put the organisation and its members ahead of justice."
This fifth report - the third on paramilitary activity - said that at the end of September last year the police discovered 10,000 rounds of IRA ammunition suitable for assault rifles "of a type not previously found in Northern Ireland and manufactured since the Belfast Agreement.
"This may have been only part of a larger consignment, and it demonstrates PIRA's continuing efforts to maintain its preparedness."
The IMC also referred to the £26.5 million alleged IRA robbery of the Northern Bank, which it has already reported on, adding that the IRA was heavily engaged in organised crime, including smuggling and "sophisticated" money-laundering.
It said that while the IRA allowed some people it had exiled to return to the republican Short Strand district in east Belfast after the murder of Mr McCartney, there was no indication that other exiled people could return to Northern Ireland.
"We have no present evidence that it [ the IRA] intends to resume a campaign of violence despite the collapse of political talks in December 2004, but its capacity remains should that become its intention."
It said the IRA carried out five "punishment" shootings and six "punishment" assaults in the six-month period to the end of February this year. Overall, the IMC said, republican paramilitaries carried out 32 such shootings and assaults, while loyalists carried out 66 such assaults.
The IMC said several questions remained relating to the IRA's and Sinn Féin's intentions, such as whether Sinn Féin sought political power in the North and South using the "paramilitary muscle" of the IRA.
"Or is it now ready to ensure that PIRA ends all forms of illegal activity and to engage wholeheartedly in democratic politics and in policing?"
The IMC said that if the IRA responded positively to Mr Gerry Adams's call on the organisation to fully embrace peace and democracy then "he will have demonstrated leadership of a high order".
The IMC said the Continuity IRA continued to be sporadically active, and that it had undertaken some reorganisation, including to its command structure. It saidthat, like the "Real IRA" (RIRA), it had no interest in calling a ceasefire.
The RIRA was the most active of the dissident republican groups and was responsible for "brutal attacks and for robbery".
It said the Irish National Liberation Army (INLA) remained a "significant terrorist group whose members had been active in violence and organised crime".
The IMC said that, while paramilitary violence was high generally, there was a downward trend in violence.
Loyalists continued to commit more violence than republicans.
While the UDA had previously stated that it planned to avoid disorder it was responsible for two murders - the killings of Darren Thompson in Derry and Stephen Nelson in Newtownabbey - and was heavily involved in organised crime.
It was also involved in targeting "in anticipation of a possible dispute with the LVF".
It was not clear if the UDA could make the transition to become a non-paramilitary force as it had pledged last autumn.
It said the Ulster Volunteer Force (UVF) and the Red Hand Commando remained active and violent. The UVF was involved in a number of attacks on Loyalist Volunteer Force (LVF) members. It continued to recruit and was engaged in organised crime.
It said the Progressive Unionist Party (PUP), which is linked to the UVF, had not done enough to prevent such activity. It recommended that Northern Secretary Peter Hain should continue financial penalties against the PUP, which cost it £120,000 in Assembly allowances.
The IMC said the LVF remained deeply involved in drug dealing, in some areas recruiting people solely for that purpose.
With the exception of drugs, the LVF was less active than previously, but retained a capacity to return to significant levels of violence.