The Provisional IRA has claimed that between 30 and 40 members were involved in the ambush that resulted in the murder of two RUC officers in March 1989.

The Smithwick Tribunal, which is investigating claims of garda collusion with the IRA in the murder of Chief Supt Harry Breen and Supt Bob Buchanan, heard today what three former volunteers said about the operation.

The former members said no garda passed information to them about the RUC officers visit to Dundalk Garda Station in March 1989.

Instead, it was described by them as a "classic IRA operation".

It started out when one person saw an RUC officer getting out of a car at Dundalk Garda Station in spring 1988.

The IRA then said it put in place a surveillance operation that involved putting people into an empty house opposite the garda station.

This continued on a casual basis until early the following year.

From purely surveillance, it then became a military operation when regular visits and patterns were noted, the tribunal was told by the former IRA members.

They identified the routes the car took and mounted an operation to "arrest, question and execute" those in the car.

They were not aware the car belonged to Supt Buchanan, but knew it belonged to some RUC officer.

They attempted to ambush the car on four separate occasions.

It involved two active service units, each with five or six members, placed in two locations close to the border where they could intercept the car after it left Dundalk Garda Station.

On the first two attempts, the car did not show up, the third attempt was aborted due to British Army helicopters being present in the area.

The fourth attempt took place on 20 March 1989. The former IRA members said that they stopped the car, but it reversed.

They opened fire killing both occupants while they were in the car. They did not know who was in the car, other than the fact they were RUC officers.

They described the shooting of Chief Supt Breen as a "bonus". He was a target for them because they believed he was involved in the ambush of IRA members at Loughgall.

The former members of the IRA told the tribunal they had convened a meeting of six people involved in the ambush to recollect the events, but the passage of time and the fact they did not keep records had affected their ability to provide exact dates and times.

Earlier, it emerged that no new intelligence has been obtained by gardaí relating to the murder of the two officers since the tribunal started.

The PSNI had said it got new intelligence about the ambush since the tribunal started and given it to Judge Smithwick.

It also emerged at the tribunal this morning that no evidence has been found to back up claims in PSNI intelligence that another, unidentified garda passed information to the IRA, which allowed them ambush the two RUC officers.

Three former garda sergeants, Owen Corrigan, Leo Colton and Finbarr Hickey, have all been questioned by the tribunal and strenuously denied any allegation of collusion.