Suspected IRA die-hards killed a Northern Ireland prison officer Thursday in a gun ambush as he drove to work, the first killing of a prison guard in nearly two decades in the British territory.

Police said a gunman in a passing car shot David Black, 52, several times as he drove onto the M1 motorway southwest of Belfast. His car plummeted down a grassy embankment into a ditch.

Police found the attackers' suspected getaway car burned out in the nearby town of Lurgan, a power base for two IRA factions opposed to Northern Ireland's peace process, the Real IRA and Continuity IRA. They said the car had Dublin license plates.

No group claimed responsibility. Politicians and police commanders said IRA militants were inevitably to blame and pilloried the various IRA splinter groups still in existence as politically pointless.

"These killers will not succeed in denying the people of Northern Ireland the peaceful, shared future they so desperately want," British Prime Minister David Cameron said in London.

The government of the neighboring Republic of Ireland pledged to help hunt down those responsible.

"I know that I speak for every decent man, woman and child on this island, north and south, in expressing revulsion at this act," Irish Foreign Minister Eamon Gilmore said in Dublin.

Gilmore said police in both parts of Ireland would crack down anew on IRA extremists, many of whom live in the Irish Republic near the border. "There will be no return to the dark and violent days of the past," he said.

In Belfast, the British Protestant and Irish Catholic leaders of Northern Ireland's unity government stood shoulder to shoulder to emphasize that no act of violence would weaken their 5-year-old coalition, the central achievement of the territory's 1998 peace accord.

First Minister Peter Robinson, a Protestant, lambasted the various IRA factions as "flat-earth fanatics, living in the dark ages, spewing out hatred from every pore."

Standing beside him Deputy First Minister Martin McGuinness, a former IRA commander, nodded in agreement and declared that Black's killers "can't kill the peace process, and we are the proof of that."

McGuinness' Irish nationalist Sinn Fein party, long a political pariah, received a share of power in Northern Ireland after the long-dominant Provisional IRA faction in 2005 disarmed and accepted that Northern Ireland's political status could be changed only by majority approval. Surveys since have consistently shown that most residents want to stay in the United Kingdom and build better relations with the Irish Republic.

Despite this, small IRA groups using myriad names continue to mount sporadic gun and bomb attacks. They usually fail because of British intelligence tipoffs or equipment failures. IRA factions have killed two civilian men this year in attacks involving turf wars over the drugs trade, and last killed a policeman in April 2011, when a Catholic recruit was blown up outside his home by a bomb hidden under his car.

The level of violence is nothing like the 1970s-'80s heyday of Northern Ireland's conflict, when typically around 100 people a year died in often tit-for-tat violence involving IRA factions and paramilitary outlaws from the Protestant side of the community.

Today about 4,000 British troops remain garrisoned in Northern Ireland — a third of their level a decade ago — but play no role in local security. Police still sometimes must patrol in armored vehicles and flak jackets, but they operate with few restrictions even in the most militant Irish nationalist districts, an impossible prospect before the Provisional IRA cease-fire.

The Northern Ireland Prison Service said Black, a married man with a son and daughter, had been a prison guard for about 30 years and was due to retire soon.

Finlay Spratt, chairman of the Northern Ireland Prison Officers Association, described Black as "a very nice fellow to work with. He always ensured he did his job to the letter."

Spratt lambasted the weakening of security provisions for prison officers, who live in civilian areas and still face death threats from extremists on both sides of Northern Ireland's sectarian divide.

He said the Northern Ireland and British governments "have stripped away all the security around prison officers. They treat us now as if we live in normal society," he said.

The victim worked at Maghaberry Prison, where more than 40 IRA inmates have been waging protests for more than a year, including smearing their cells with their own excrement. The prisoners chiefly want to overturn the prison's policy of strip-searching inmates.

The IRA factions particularly seek to deter Catholic recruitment into the once Protestant-dominated police force, a major achievement of peacemaking.

But Catholic recruitment into the similarly Protestant prison service has been less successful, a problem highlighted in a recent British government appeal for more applicants from Irish nationalist communities.

Black was the 30th prison officer to die as part of Northern Ireland's four-decade conflict. Most were killed by the Provisional IRA, but the previous killing in 1993 was committed by the Ulster Volunteer Force, a paramilitary group rooted in the British Protestant side of the community.

Spratt said Black's killing was unlikely to be the last IRA attempt to kill prison officers — and was likely to deter people from seeking work as one.

"Why would you come and work in the prison service now and chance your life for 18,000 pounds a year?" he said, referring to the starting base salary, equivalent to $29,000.