The dissident republican Real IRA has emerged as one of the most dangerous groups opposed to the Good Friday settlement.
It is reportedly led by the man who resigned as the IRA's quartermaster-general in October 1997 after he broke with Sinn Fein because of its support for the Good Friday Agreement. Security forces estimate that its membership is between 100 and 200. It is thought to have access to Provisional IRA explosives and detonators. Some of its members were leading IRA bomb-makers.
The Real IRA was responsible for the Omagh bombing on 15 August 1998 in which 29 people died. The group apologised for the civilian deaths, claiming it was aiming for commercial targets.
It also is believed to be responsible for a series of attacks, including a 500lb car bomb which devastated the market town of Banbridge, Co Down, in August 1998. In May 1998, following a mortar attack on a police station in Co Fermanagh, it declared that a "war machine is once again being directed at the British Cabinet".
The Real IRA called a ceasefire less than a month after the Omagh atrocity. The ceasefire has not been recognised.