Update 4:50pm: Armed Support Units will be in place across the country by the end of the year.
The Garda Commission has said that while Ireland is a very safe place, we have a domestic terrorism threat that has not gone away.
Nóirín O'Sullivan was speaking at a Garda training exercise in Dublin's Docklands that simulated a terrorist attack.
The Commissioner says she believes that officers have a quick response time to incidents
"We've had a number of real life events unfortuantely over the last few weeks for example, at the Dart station, we saw an individual on a train prodcued what turned out to be an imitation pistol," she said.
"We are measuring all of the response times and we are very confident that we have the response capability."
Update 3.30pm: The Garda Commissioner says that Ireland is a very safe place but we have to be realistic.
Noirin O'Sullivan was speaking at a garda terrorist training exercise in Dublin's Docklands.
Commissioner O'Sullivan says she is confident that we have the response capability in the event of an attack, but that officers are learning lessons all the time.
She added that there will be armed support units for all of Ireland by the end of the year.
"The armed support unit was introduced in December for the city here. We then gave a commitment that we are going to increase our armed support units all over the country.
"That will be completed by the end of this year. We have increased the numbers here in the city because what we're simulating here today is an international terrorist threat.
"But what we have to remember is that we also a domestic terrorist threat which hasn't gone away"
Earlier:: Specialist Garda units have carried out a simulated anti-terror operation in central Dublin.
The exercise involved attackers targeting people at the Docklands railway station before taking hostages on a train.
The operation was partly designed to measure response times for elite Garda units and involved officers reacting to victims of knife attacks and confronting armed terrorists.
Justice Minister Charlie Flanagan said he hoped the exercise would give the public reassurance.
"While a terrorist attack here may be unlikely, the authorities are in no way complacent in the measures being taken to respond to that threat," he said.
"The exercise today is part of an ongoing process of planning and training that, to a large extent, takes place quietly and behind the scenes. That said, this work goes on relentlessly."
The exercise began with a simulated report of a car crash at Spencer Dock to which local units were dispatched.
The scene they were confronted with included an injured person on the ground and people having been stabbed.
The officers were also told of a report of two attackers - one armed with a gun and one a knife.
The exercise then moved inside the station.