Update 3.30pm: Victims from 34 countries were killed or injured in the Spain terror attacks, a Spanish ambassador said.
Jose Maria Rodriguez Coso heads the diplomatic presence in Ireland.
He said injuries to Irish holidaymakers from the attacks were not as serious as some, but added the multiple nationalities of those caught up in the violence showed its global nature.
"They are trying to strike against the core of our way of living, our way of living and enjoying life.
"That is why we need the strength and the help of friends like Ireland to continue our job.
"Because terror will not prevail, we will continue to live our lives, we will continue receiving guests and doing our job as we did in the past even in the worst of moments."
Almost two million Irish visitors are expected in Spain this year.
The ambassador said the Irish shared his compatriots' traits of strength and endurance against adversity.
"It is another element of cultural community, very difficult pasts sometimes ... make you stronger.
"I think that is one of the reasons we have done so well, because we have lots of very strong character."
Many Spaniards come to Ireland to work or attend university.
The diplomat added: "There is a very strong movement amongst both countries and that is natural.
"Most of the Irish know Spain or have been there at least once in their lives."
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."
"Nobody really knew how to get home, the metros were closed, nobody knew what bus to get, the taxis were all full and all their lights were turned off.
"So that was a wee bit like, 'how are we going to get home and is it even safe to be on the street?'"
Update - 9.15am: A five-year-old Irish boy suffered a broken leg when his family was caught up in the terror attack in Barcelona.
The boy's father also has leg injuries after a van was driven into innocent people in Las Ramblas, one of the busiest avenues in the Spanish city.
Ireland's Foreign Affairs Minister, Simon Coveney, said: "They are not life-threatening, I'm relieved to say.
"But in a way it's a miracle that more Irish people weren't involved, given that there are so many Irish people in Spain, Barcelona and Cambrils at this time of year."
The father and son were part a family of four, including the mother and a daughter, and are understood to have been on a trip to celebrate the boy's birthday.
The youngster suffered a broken femur.
The mother and father are understood to be from Cebu in the Philippines and are naturalised Irish citizens. They hold dual citizenship. The children were born in Ireland.
The Department of Foreign Affairs is assisting the family.
Earlier: An Irish family were caught up in the terror attack in Barcelona.
The mother and father are originally from the Philippines and are naturalised Irish citizens, while their two children were both born in Ireland.
It is understood they were holidaying in the Spanish city for the birthday of one of the children.
It is reported one of the family members sustained serious but non life-threatening injuries.
The Department of Foreign Affairs is assisting the family. Its officials opened a hotline for anyone concerned about relatives in Spain on 01-408 2000, while the Irish Embassy in Madrid is also fielding calls on +34 9143 64093.
President Michael D Higgins led condemnation of the attack and sent a message of condolence.
"Barcelona has a long history of hospitality and has over the years received so many people from around the world," he said.
"As President of Ireland, I want to send the people of this great and welcoming city not only our sympathy but also the solidarity of the people of Ireland."
Taoiseach Leo Varadkar said: "An attack of this nature, targeting the people of Barcelona and visitors enjoying that wonderful city in the height of the tourist season, is both wanton and cowardly and has no place in our society.
"At this time of immense grief, I want to offer our solidarity and support to the people of Spain, with whom we have such close relations."
Foreign Affairs Minister Simon Coveney said he was appalled by the attack.
"On behalf of the Irish Government, I wish to convey our condolences and solidarity with the people of Spain at this time," he said.
Justice Minister Charlie Flanagan described it as an unspeakable act of terrorism and vowed that gardai would liaise closely with Spanish counterparts.
"It is clear that the intention of those who carried out this appalling, evil act was to kill, wound and terrorise innocent people enjoying the freedoms we share and cherish," he said.
"Our thoughts are with the victims and their families."