The home secretary has said a pipe bomb found in a car at Belfast International Airport was the 38th dissident republican attack this year.
In a speech in Whitehall, Theresa May said the device had been planted by "residual terrorist groups" and was intended to cause civilian casualties.
She added that she was liaising closely with the director-general of MI5 Jonathan Evans to combat the threat.
It is understood the bomb may have been there for up to a year.
It was found on Saturday in a vehicle that had been in the long-stay car park since 2009 and was about to be towed away.
Suspected flammable liquid was found along with the viable device, police said.
There have been calls for an overhaul of security arrangements at the airport since the bomb was discovered.
It is believed the incident was not linked to bombs left on US-bound cargo planes.
On Monday, police said they were investigating a link to dissident republicans as "one line of enquiry".