Analysis: Ulster crisis over IRA's 'infiltrator'

The sight of heavily-armed police raiding Sinn Fein offices in Belfast's government buildings yesterday created a political furore which threatened to engulf the already ailing Northern Ireland peace process.

Angry protests from Sinn Fein were countered by a government assessment that a republican infiltrator had provided the IRA with hundreds of confidential documents. Thiswas denounced by hardline Unionists as the last straw and, potentially, it could guarantee success for their campaign to force Sinn Fein out of government.

Although a clearly angry First Minister and Ulster Unionist Party leader called on the Government to act, David Trimble stopped short of leading his party out of the executive in which his ministers sit side-by-side with Sinn Fein.

But hardliners were delighted at a development which most Protestants will see as clinching their argument that the republicans are unreconstructed terrorists who readily resort to illegal methods.

Four people, one of them a woman, were arrested in swoops involving 200 police officers in north and west Belfast. One of the four is a former messenger who worked for the Northern Ireland Office in Castle Buildings, which holds the offices of the Secretary of State for Northern Ireland, John Reid, and junior ministers. The authorities believe that an IRA "mole" worked as a messenger in the offices for over a year before being uncovered in September last year. He is said to have been discovered photocopying documents.

The messenger's role was to deliver documents from office to office, and to deal with mail to and from the NIO. This included ministerial correspondence. Some of this went to Downing Street, while others went to the Irish government and other destinations.

Meanwhile, angry Colombians yesterday shouted insults and waved placards at lawyers representing the three Irishmen on trial in Bogota accused of involvement with narco-terrorists.

About 20 members of the Wounded Colombia group screamed "Killers" and brandished banners saying "IRA, go home and kill your own people" at the lawyers for James Monaghan, Niall Connolly and Martin McCauley.

But the IRA suspects themselves – who are charged with training rebels and using false passports to enter Colombia – avoided the heated scenes outside the nine-storey brick building in a Bogota side-street by refusing to leave their cells for the first day of the trial.

Their absence, which further enraged protesters, meant that the judge, who had been due to rule on the evidence, was forced to postpone the hearing until 16 October. They each face 15 to 20 years in prison if convicted.

The three men, who are accused of teaching bomb-making techniques to Marxist rebels, were arrested at Bogota airport 14 months ago after visiting a rebel stronghold in southern Colombia.

The allegation that foreigners were helping rebels who have waged war against a succession of elected governments for 38 years has incensed many Colombians, including Wounded Colombia leader, Juan Carlos Pulido. He said: "We find it intolerable that the IRA is coming to Colombia."

However, on Thursday, defence lawyers claimed that the Colombian government had "trumped up" the charges in an attempt to capitalise on the case for more counter-terrorism aid from the United States.

The men's lawyers say that the case is based on scant evidence and full of procedural errors, including the fact that the three were arrested by military officials who do not have the power to make arrests.