Gardaí are investigating the discovery of a 70lb bomb inside the house of a prominent Irish businessman last night.
The device was found out the house of former senator Dr Edward Haughey near the Louth/Armagh border.
It is understood an attempt was made to detonate the bomb which was a homemade device capable of demolishing the Dr Haughey's Dungooley property.
"It would have flattened the house, or certainly most of it, and it would have killed anybody in the vicinity," one source told the Irish Times.
It is not yet known why Mr Haughey's property was targetted but he is understood to helping a joint Garda/PSNI team with their inquiries.
One theory is that the incident is related to a recent upturn in 'Real IRA' activity that has seen shops in Newry, Co. Down, firebombed and devices placed on the Belfast-Dublin rail line.
A major cross-Border security operation was in place last night involving Garda and PSNI checkpoints along the Border.
The bomb was found yesterday lunchtime in a downstairs room of the property, which is undergoing renovations and has no roof or windows.
The perpetrators attempted, but failed, to detonate the device from a laneway 90 feet away. The device was made safe by the bomb-disposal squad and taken for examination.
Taoiseach Bertie Ahern said in a statement last night: "The matter is currently the subject of a Garda investigation. Any such incident is a matter of concern and is to be condemned."