Update - 10.50am: The Minister for Foreign Affairs, Simon Coveney, says Ireland is better prepared than we have ever been for a terrorist attack.
Mr Coveney says while we need to remain vigilant, the risk of an attack remains possible, but not likely.
He said: "We need to work to make sure incidents like this don't happen in Ireland, but should something happen, that we have the training and the resources and the focus to respond.
"But of course when you have a madman willing to drive a van into a crowded street it is very difficult to prepare and to respond to that."
Irish man David Roche was on Las Ramblas with his children yesterday.
He describes what happened, saying: "We heard this bang and people started to run and scream, it was very hysterical.
"Every now and again there would be a surge of people starting to run, not knowing how these people operate, you had to run with the crowds."
Dublin's Lord Mayor, Mícheál Mac Donncha, has opened a Book of Condolence for the victims of the tragedy in Barcelona.
The public will be able to sign the Book of Condolence at The Mansion House, Dawson Street as follows:
* Friday 18th August 12pm – 4pm
* Saturday 19th August 12pm – 4pm
* Monday 21st August 10am – 4pm
Lord Mayor Mac Donncha said: "I was horrified to hear about the attacks on the people of Barcelona and Cambrils. Dublin and Barcelona have been sister cities since 1998 and have developed close ties throughout the years.
"I am opening this Book of Condolence to let the people of Dublin express their sympathies and solidarity to the families of those who died or were injured and to stand with the people of Barcelona.
The Lord Mayor of Cork, Cllr Tony Fitzgerald, will also open a Book of Condolence at 3pm today in The Atrium of City Hall.
The Lord Mayor said: "On behalf of the people of Cork city, I wish to convey our condolences and solidarity with the people of Spain at this time. My thoughts are with the families and friends of all those who have lost loved ones and those who were injured.
"We stand with the people of Barcelona and Spain."
The Book of Condolences will remain open in Cork until Friday, September 1, 2017.
Update - 9.51am: Amy McColgan from Letterkenny in Donegal was in Barcelona at the time of yesterday's terror attack and describes what she saw.
She said: "Whenever they decided to lift the shutters and let us out, there was nobody on the streets, it was eerie, very eerie.
"There was a tent and the police had the tape across and they were ushering us to get us off that street that was closed off.
"And that was scary now, because we still didn't know what was going on."