The New IRA - which has accepted responsibility for the murder of journalist Lyra McKee - is the biggest of the dissident republican groups operating in Northern Ireland.
It has been linked with four murders, including PC Ronan Kerr, who was killed by an under-car bomb in Omagh in 2011.
The group is also linked to the deaths of prison officers David Black, who was shot as he drove to work at Maghaberry prison in 2012, and Adrian Ismay, who died in 2016 after a bomb exploded under his van outside his home in east Belfast.
The New IRA is believed to have been formed between 2011 and 2012 following the merger of a number of smaller groups, including the Real IRA - the group behind the 1998 Omagh bomb.
It is strongest in Londonderry, north and west Belfast, Strabane and other pockets in Co Tyrone, and Lurgan in Co Armagh. This year the group was responsible for a car bomb outside the courthouse in Bishop Street, Derry.
The explosives-laden car was left on the city centre street on a Saturday night in January, and scores of people, including a group of teenagers, had walked past before it detonated.
The New IRA also claimed a number package bombs posted to targets in London and Glasgow in March.