Is IRA a pressure group?

Can terrorists or an armed organization be a pressure group? ''Normal'' pressure groups try to influence media or government policy using peaceful methods. They can write letters, organise protests or advise politicians during the legislative process. They can represent various causes or interests of their members. They can even use illegal actions to achieve their goal. But they never use violence. On the other hand the IRA(or ETA or any other armed group) use terror to make their statements clear and well heard. They can also influence the media or the government. Sometimes they meet with extreme success like in Spain where presumably Al-Queda changed the result of the parliament elections by bombing trains in Madrid. People were angry about their current government, Partido Popular and voted for PSOE instead. The IRA used terrorist actions to bring chaos into the Northern Ireland government and cause as many casualties as possible for British soldiers and officials. They hoped that huge losses would force Britain to withdraw their presence from the north. They also wanted to influence the British media.
Even though they didn`t meet with much success , famous military actions like the assassination of Lord Louis Mountbatten and Warrenpoint ambush attracted media attention from all around the world.
In my opinion groups that use violence and terror to achieve political goals aren`t pressure groups sensu stricto. Of course they make a serious impact on societies and politics but the means of pressure they use, exclude them from being pressure groups and are considered by most of the people as terrorist or armed organisations