Catholic extremists used remote-control technology to set off a bomb that has left a Catholic, Gaelic-speaking Northern Ireland police officer fighting for his life, the Observer has learned.

A former Provisional IRA bomb-maker recruited to Oglaigh na hEireann (ONH), one of three dissident groups opposed to the peace process, had tested the remote mechanism with a car bomb two months earlier at the Policing Board's Belfast headquarters. A device inside the car, left at the board's offices in Clarendon Dock, had been triggered by remote control.

The attack on 8 January left Peadar Heffron, a Police Service of Northern Ireland (PSNI) Gaelic football player, in a critical condition. One of his legs has been amputated and he has not regained consciousness. He suffered what are described as "horrific injuries" to his lower body, and surgeons had to remove his bowel.

Heffron was severely injured when the bomb exploded under his car, about a mile from his home near Randals­town, Co Antrim. At the time he was on his way into west Belfast, where he works at a police station. ONH, a breakaway faction of the Real IRA that includes former Provisionals, later admitted it carried out the attack.

Heffron has personified the radical changes within policing in Northern Ireland over the past decade. Ten years ago, it would have been unthinkable that a Gaelic-speaking GAA player from a nationalist redoubt would join the police. It is also why the ONH is understood to have spent months targeting him. Security sources have told the Observer that a unit of ONH based in the Andersonstown area of west Belfast is suspected of gathering intelligence on the officer's movements before placing the bomb under his car.

It was also an indirect attack on Sinn Féin, because not only does the party now urges nationalists to join the PSNI, Heffron's cousin is Declan Kearney, who is Sinn Féin's national chairman and is regarded as one of the party's key backroom strategists.

In a ghoulish response to the attack, a dissident republican source said ONH regarded the attack as a success: "The bomb was less than a pound of Semtex, but it was big enough to kill. A mercury tilt switch wasn't used, a remote control activated the device after the target drove past in his car. The leadership are happy with the outcome."

Security sources are concerned that ONH has "burned up the technology curve" with this latest innovation. Last week the PSNI issued special mirrors to 10,000 of its officers and civilian staff to check under their vehicles for bombs. Some officers may be offered electronic detectors, according to the PSNI commanders. Assistant Chief Constable Duncan McCausland stressed, however, that the best way to counter the new threat was for all PSNI staff to look beneath their vehicles and check for devices planted under them.

Although the Provisional IRA used remote-control technology to set off landmines and other improvised devices, they preferred using the mercury tilt switch for triggering under-car booby-trap bombs.

The Real IRA, Continuity IRA and ONH are replicating the Provisional IRA during the Troubles. From the beginning of the conflict in 1969, Catholic police officers were targeted to deter nationalists from joining the security forces and thus portraying the police in particular as a wholly Protestant and unionist force.