Fuse was lit on bomb under car
The fuse on an under-car pipe bomb which failed to explode at the family home of a Catholic police officer had been lit.
Dissident republican group the Real IRA is the chief suspect for planting the device which was discovered on Sunday night in a nationalist estate in Londonderry, the region's second largest city.
The bomb was under a vehicle that belonged to the policeman's parents. This is the second time they have been targeted but the elderly couple have vowed to stay at the house, Superintendent Chris Yates said.
Earlier this month the outlawed Real IRA vowed to try to kill more police officers during a rally in the city.
The Police Service of Northern Ireland's Mr Yates said: "This is the equivalent of a military hand grenade." He pledged to leave no stone unturned to try to identify those who planned the attack and appealed for information from the community.
The couple, from Drumleck Drive in Shantallow, are pensioners. Their home was attacked by the Real IRA in 2009 using a similar device but Mr Yates said they remained unbowed.
He said: "The device had been initiated; it had the fuse lit on it but it failed to fully explode. We are treating it as a terrorist investigation and as attempted murder because anyone next to this when it exploded would have been seriously injured and possibly killed."
Dissident republicans have targeted police several times. New constable Ronan Kerr was killed when a device blew up under his car in Omagh, Co Tyrone, last April.
Ministers and senior police have warned the threat level remains severe. Derry has been named UK Capital of Culture for 2013. In October the office established to organise the celebrations was targeted for the second time by dissident republicans.
On speaking to the police officer whose parents were targeted, Mr Yates said: "He is showing a remarkable resolve. He has no intention of changing his chosen profession."