We'll be closely monitoring any information with regard to the activities and affiliations of those three men

Philip Reeker, US State Department

He said any relationship with the FARC or with any other paramilitary organisation "would certainly raise troubling questions".

"We'll be closely monitoring any information with regard to the activities and affiliations of those three men who have been arrested in Colombia."

The three suspects can be held until next week before either being charged or released.

Colombian prosecutors have said they are advancing with their investigation into the three men who are accused of training Marxist rebels.

However, the Colombian army has now admitted it does not have secret film of the trio.

It is thought they may also have been exchanging information before they were arrested at the weekend after entering the country in June.

Background

Martin McCauley won five-figure sum in damages against RUC after shoot-to-kill incident He received a suspended sentence for possessing rifles James Monaghan appeared on party platform at 1989 Sinn Fein conference

The leader of the nationalist SDLP, John Hume, has said Sinn Fein needs to clarify the republican position in light of the Colombian arrests.

Mr Hume said the revelations could be damaging to the political situation.

Sinn Fein's Conor Murphy likened the allegations to "candyfloss" and said they should not be used to block demilitarisation.

"I regret that people have used the story that they found on the other side of the world to try to undermine the peace process here," he said.

International law

If convicted, the trio could face maximum prison terms of 15-20 years, court sources in Colombia have said. However, they could be deported or extradited.

Colombia's minister of defence said: "We are advancing with the investigation, the British authorities are aware and the procedures of international law will be followed."

Two of the men were travelling on British passports, the other was holding an Irish passport.

The arrests were made by a specialist investigative branch of the Colombian Police, known as the Fiscalia, at the weekend.

Colombian Commander-General Jorge Enrique Mora told the BBC: "It has been confirmed to us by the authorities in Northern Ireland that they are IRA."