Eight post offices have been targeted by armed raiders nationwide since the start of last month leading to calls for An Post to carry out a review of its security procedures.
Sources have said there is concern among gardai that the glass partitions in post office counters are "not secure enough" after a number were smashed open by criminals during recent robberies.
Of the eight armed raids since December 1, two happened last Tuesday in Dublin.
In the first, at around 9am at Jobstown post office on Kiltalown Road, Tallaght, two men armed with a sledgehammer and a machete took the contents of the till before making off in a grey Mitsubishi Spacestar.
Thirty minutes later, shots were fired during an armed robbery at Roebuck post office in Dundrum.
After entering the premises, one of two men fired shots that shattered the glass partition at the counter.
He then jumped over the counter and stole an amount of cash. The second man took money from a cash register.
The pair then fled in a stolen Subaru, which was later found near Mount Carmel Road in Goatstown.
While these were the first armed post office robberies of 2016, there were six in December.
At 2.30pm on December 23, three men were arrested after a robbery at the post office in Athboy, Co Meath, in which one raider was armed with a sawn-off shotgun.
A sum of cash, believed to be several thousand euro, was handed over and three men fled the scene in a car, but it crashed a short distance away.
Two days earlier, the Bawnogue post office in Clondalkin was the target of a raid in which a sledgehammer was used to smash a glass partition.
On December 17, the Killinarden Post Office in Tall- aght was targeted, and sources said gardai are investigating whether the same local gang responsible for this robbery were also behind the Jobstown raid.
On December 12, the post office in Crosshaven, Cork, was targeted, while on December 3, three men were arrested after a botched robbery at the Leonard's Corner post office in south inner city Dublin.
At about 12.30pm, three masked men armed with knives, a crowbar and other weapons entered the post office before threatening customers and staff.
They failed in their attempts to open a safe and fled empty-handed.
A post office in Carlow town was also targeted on December 1.