Two armed garda regional support units came into operation in Cork and Limerick today, to provide back-up to frontline gardaí in critical incidents.

The units are second-tier firearms response teams and are made up of uniformed gardaí, who will arm themselves and change into tactical outfits in response to an emergency call.

The Garda Commissioner Fachtna Murphy says these units have been set up to respond to critical incidents such as gun attacks and hostage incidents.

The first two will operate on a pilot basis with units subsequently to be established in all five garda regions outside Dublin.

The Association of Garda Sergeants and Inspectors says its members will co-operate with the programme but it has serious concerns about the units.

It is worried about the time it will take for uniformed gardaí to change into armed response units and about the principal of arming what were previously unarmed officers.

Instead it has called for the establishment of permanent, dedicated armed response units in all garda divisions.