Timeline of dissident republican activity
April 2011 -- PSNI Constable Ronan Kerr killed by undercar booby-trap device.
December 2010 -- Policeman finds unexploded grenade outside his Co Fermanagh home.
October 2010 -- Car bomb explodes on Derry's Culmore Road.
August 2010 -- Three children injured when bomb explodes in Lurgan, Co Armagh; booby trap device partially explodes under car of former policeman; and bomb planted under the car of female police officer in Kilkeel, Co Down.
February 2010 -- Real IRA man Kieran Doherty found shot dead in Derry. RIRA said they killed him.
January 2010 -- Constable Peadar Heffron (33) seriously injured when an undercar bomb explodes.
October 2009 -- Police officer's partner injured when a bomb explodes under her car in east Belfast.
March 2009 -- Constable Stephen Carroll shot dead by CIRA in Craigavon, Co Armagh.
March 2009 -- Sappers Patrick Azimkar and Mark Quinsey are gunned down outside army barracks in Antrim.