Police in Belfast and Bogota, the Colombian capital, said all three were traveling on false passports, had spent several weeks in a rebel-controlled area, and had traces of explosives and cocaine on their clothing.
Police said James Monaghan, in his late 50s, had been convicted of possessing IRA explosives and conspiring to cause explosions in 1971. He has been identified as the IRA's ''education officer'' in charge of identifying new weapons-making techniques, Monaghan said.
Martin McCauley, 40, was shot in a 1982 police ambush at a farmhouse containing IRA weapons, and later received a suspended two-year sentence for arms possession.
The third man hadn't been postively identified, but police in Colombia had forwarded fingerprints and other evidence to police in Belfast.
The IRA has previously traded its terrorist expertise for weapons, particularly in Libya.
Britain's secretary of state for Northern Ireland, John Reid, said he was disappointed that the IRA had ''moved away from a supposedly historic commitment when the ink was barely dry.'' He said it would ''give comfort and succor to those who have been very skeptical about the IRA's intentions, particularly given the news reports out of Colombia.''
Irish Prime Minister Bertie Ahern said he was disappointed too. ''Putting arms beyond use is an indispensable part of implementing the Good Friday agreement,'' he said.
Britain and Ireland jointly unveiled plans Aug. 1 designed to meet key Catholic demands and spur IRA disarmament.
Britain specified further military cutbacks and promised more changes to the predominantly Protestant police force, the Royal Ulster Constabulary. A 175-point plan on changing the RUC into a more Catholic-friendly Police Service was expected to be published soon.
Tuesday's IRA move mirrors its behavior in February 2000, when Britain stripped power from local hands to shore up Ulster Unionist leader David Trimble, the senior minister in the Northern Ireland administration.
Hours before Trimble's expected resignation, the IRA told disarmament chiefs about the ''context'' in which it would give up weapons. Britain rejected that offer as hopelessly vague, and the IRA immediately withdrew it.
In May 2000, Ulster Unionists agreed to resume work alongside Sinn Fein after the IRA pledged to put arms ''completely and verifiably beyond use.'' But Trimble resigned from his post six weeks ago when a second deadline for IRA disarmament passed.