A group calling itself the "IRA" said it was responsible for placing the car bomb which detonated outside the courthouse in Derry on 19 January in a statement sent to the Derry Journal.

"We also caution those who collaborate with the British that they are to desist immediately as no more warnings will be given," the statement said.

The PSNI has said its main line of inquiry is that the bomb and a spate of security alerts in the city two days later were conducted by the New IRA, an amalgamation of dissident republican factions in Derry, who were allegedly responsible for the riots in the Bogside area of the city during the summer

Police said a number of young people walked past bomb the moments before it exploded outside the courthouse, which the PSNI said was a "clear demonstration" that the bombers "do not care about the safety of those living in this community".