Other Unionist reaction: Ulster Unionist leader Sir Reg Empey claimed the decommissioning and its procedure had failed to maximise public confidence.
"Unionists remain to be convinced of the republican movement's commitment to exclusively peaceful and democratic means," he said.
Describing the IRA move as a "dramatic U-turn by the republican movement from their stated position of 'not a bullet, not an ounce'," he added: "We will wait and see the outworking of events. It is imperative that not only arms are decommissioned but that the dismantling of the republican movement's criminal empire is also completed."
Sir Reg called on the British government to publish an estimated size of the IRA arsenal given to it by the de Chastelain commission. Lord Kilclooney, another senior UUP figure, said the decommissioning was "major and significant" and represented "real progress to a peaceful and democratic Northern Ireland".
However, he warned: "The IRA still exists and it may still have retained some illegal arms. Clearly some considerable time will be required to assure unionists that the IRA is no longer a threat to them. In the meantime, Sinn Féin cannot be in government or in membership of the Policing Board."