The unidentified militants killed three journalists, two Spanish and one Irish, in the eastern region of the country, which has been witnessing an increasing number of attacks by armed groups, some affiliated with al Qaeda and others with the Daesh.
The attack in the Springfield Road area followed a night of rioting by nationalists and pro-British loyalists nearby in the Northern Ireland city on Wednesday that was condemned by the British and Irish governments and local political leaders.
Citing Brexit as their reason, loyalist paramilitaries, including outlawed groups, pull back support for Northern Ireland's 1998 peace deal that ended violence between groups fighting for a united Ireland and those opting to stay with the UK.
Irish PM Micheal Martin says the country must "face up to the full truth of our past," as a long-awaited report recounted decades of harm done by church-run homes for unmarried women and their babies, where thousands of infants died.