Secretary of State Theresa Villiers has paid tribute to postal workers for facing a "despicable" risk after intercepting a letter-bomb at Stormont Castle.
She said that although her "name was on that letter", the "people who were really at risk were those who handled the parcel en route", including "very brave individuals" in the post room.
She said: "I would pay tribute to them. I think it's despicable that people who are just turning up for a day's work could find themselves at risk as a result of the activities of dissident republicans."
Taking questions from members of the Northern Ireland Affairs Select Committee, the Secretary of State said the security situation in Northern Ireland "continues to be a grave concern".
"The threat level remains at severe, as it has been for several years now," she said. "We have of course seen a number of attempted attacks and a number of very disruptive hoaxes over recent weeks, and my feeling is that the severity of the threat hasn't gone up, but that it continues to be a significant level of severity.
"These things tend to be cyclical and the reality is, sadly, that even at times when the attacks aren't necessarily being reported by the newspapers, there is continuous planning and targeting by dissident republicans."
Asked about the Richard Haass talks on issues left over from the peace process, Ms Villiers also warned that Northern Ireland continued to "pay the price of these divisions".
She said: "There is generally an economic price that is attached to continuing tensions around these issues. It would be very positive for Northern Ireland, for the quality of life and for the economy if progress could be made on these issues, and if it's not then certainly it would hold back progress on building social cohesion and the economy."
But the Secretary of State said she remained "pretty optimistic" that the talks would be successful. "Dr Haass has set himself a timetable," she told MPs. "He is a very impressive individual, he is determined and there have been a lot of positive signals from local parties that they are willing to make progress."
Ms Villiers also said "legislation might be required" depending on what Dr Haass suggested about the Parades Commission.