The IRA and the Basque ETA helped left-wing terrorists who killed 35 people in a bomb attack on a night-club in Colombia last weekend, the country's Minister for Defence has alleged.
The charge was made as the US Secretary of State, Mr Colin Powell, urged Congress to offer the Colombian authorities an extra $574.6 million to fight the FARC guerrillas.
The attack late last Friday destroyed a 10-storey building in Bogota, killing 35 people and wounding 162 more, many of them women and children.
"This is something more sophisticated than we have seen in the past," the Defence Minister, Ms Martha Lucía Ramírez, said in Washington after she arrived for a round of talks with Bush administration officials.
The bombing of Bogota's most fashionable night-club occurred shortly after the end of the latest phase of the trial of three Irishmen, Mr James Monaghan, Mr Niall Connolly and Mr Martin McCauley.
They have been held in jail since they were arrested travelling on false Irish passports in August 2001 and are facing trial on charges that they offered bomb-making advice to FARC.
Questioned about the latest allegations that the IRA has co-operated with FARC, the Sinn Féin president, Mr Gerry Adams, speaking in Dublin, said: "I don't put any credence in these reports. Since these three Irishmen were arrested, the entire case has been scattered with claims that have not been substantiated.
"I would be entirely sceptical about all of this," he told The Irish Times.
Last week President Alvaro Uribe was criticised by Sinn Féin after he said the Colombian authorities had "three men in jail who had come to help the FARC".
The Club El Nogal attack has deeply shocked Colombia's wealthy elite, which suffered less than rural dwellers during the 40-year conflict that has left tens of thousands dead.
A Jeep Cherokee packed with 330lb of explosives detonated on the third floor of the building, killing six children and 29 adults, including a number of staff members of the club.
Colombia on Wednesday sought a meeting of the permanent council of ambassadors to the Organisation of American States to hear a report on the attack from Vice-President Francisco Santosa.
Blaming FARC, Ms Ramírez said it had imported bomb-making skills through "strategic alliances with other groups", including the IRA and Basque separatists.
The extra US aid, said the Secretary of State, would "secure democracy, extend security and restore economic prosperity to Colombia, and prevent the narco-terrorists from spreading instability to the broader Andean region". The Colombian authorities had sought even more money.