DISSIDENT Republicans have been blamed for a bomb attack that seriously injured a Catholic policeman in Northern Ireland.The off-duty police officer was injured after a booby-trap bomb exploded underneath his car as he left a house at Spamount village outside Castlederg, Co. Tyrone shortly after 9:30 p.m. on Monday night.The officer's life is thought to have been saved after he was dragged from his burning car by local residents. He later underwent emergency surgery, but his injuries are not thought to be life-threatening.Dissident Republican activity in the Strabane/Derry area has been high in recent months. Last weekend dissidents were blamed for an incendiary device planted in a Co. Tyrone toy store.In February dissidents were blamed for the murder of former member Andrew Burns on the Strabane/Donegal border.In November of last year the Real IRA was blamed for guns attacks on off-duty police officers in Derry and Dungannon.However, it is the apparent newly acquired sophistication of Monday's car bomb that is understood to be causing police most concern.Security sources are understood to be looking at whether dissidents may have used a mercury-tilt switch device in Monday's bomb attack.While the IRA regularly used mercury-tilt switches during the Troubles, dissidents were, until now, thought to lack the expertise needed to use such devices successfully.Police Service of Northern Ireland (PSNI) Chief Constable Hugh Orde condemned the attack, insisting that dissidents were being increasingly isolated by the community."This was another attack by a group trying to unravel everything that has been achieved. "They have not defeated the police service for the last 38 years, and if they seriously think this sort of event is going to defeat the PSNI they are badly mistaken," he said.Orde claimed dissidents were now more dangerous as they were in their "end game.""Every political party has signed up to policing, everyone wants to move on. "We had a major investment conference last week - this place is moving in the right direction and I think these people realize that," Orde said.Secretary of State Shaun Woodward described those responsible for the attack as "contemptible.""The contrast between the PSNI officer, dedicated to serving the community, and those with no politics, no support and no principles, who carried this cowardly attack could not be clearer," he said."As Northern Ireland moves towards a new and better future, there remains a tiny minority of contemptible, criminal elements who have been rejected by the people, north and south. They will not be allowed to stand in the way of progress."Sinn Fein's West Tyrone MP Pat Doherty said that dissidents had no popular support within the Nationalist community for their continued campaign."This attack has to be absolutely condemned," he said."These people have no popular support. We have moved on, there is no turning back to the old days."