Mr David Trimble has met Colombian officials over the case of three IRA suspects detained in the South American state on suspicion of training left-wing rebels.
Colombian authorities have alleged the three Irishmen - Mr Martin McCauley, Mr James Monaghan and Mr Niall Connolly - trained FARC guerrillas in bomb-making techniques and that IRA technology has been used in the country's civil war.
The Northern Ireland First Minister met Colombian vice-president Mr Francisco Santos on the fringes of the Earth Summit in Joannesburg, South Africa.
The talks covered several issues of common concern, he said, including the issue of the exchange of bomb-making knowledge between the IRA and left-wing rebels.
"I think there is no doubt that there has been a transfer of technology to the narco-terrorists," the First Minister said. "It is not clear what the reasons for this were and what people intend to do about it in the future.
"That is something that the Republican Movement must address and only the Republican Movement can clear that up".
Mr Trimble would not be drawn on the case against the three detained in Bogota. He called on republicans to do the same as legal proceedings drew near.
The three men have been held since last August by the Colombian authorities after they were arrested trying to leave the country following a visit to a zone controlled by the Marxist FARC militia.
Mr Trimble was criticised by Sinn Féin for meeting the Colombian vice president.
North Belfast MLA Mr Gerry Kelly attacked the Ulster Unionist leader, accusing him of 'deliberately prejudicing the right to a fair trial' in Colombia of the three republicans.
PA