Update 12.40pm: President Michael D. Higgins has condemned the attacks in Berlin, Ankara and at a Zürich mosque.
President Higgins said: "The attacks are calculated to sow fear at the heart of our societies", urging solidarity on this International Human Solidarity Day.
He added that "We must strengthen our resolve not to let such attacks undermine the way of life in our global community, seeking to live in diversity and peace."
Irish citizens have been urged to check in with family at home and let them know they're safe, in the wake of the Berlin attack.
Irishman Killian McDonagh walked through the scene of the attack just a short time before it happened, and said he believes Berlin has become a target for this kind of incident.
"People in Germany have been expecting this, because Germany has recently been the moral leader of the free world," he said. "The lifestyle that people have here is envied all over the world.
"In many ways, people here were expecting this to happen and in many ways, it's just good that it wasn't worse than it was."
Irish Ambassador to Germany Michael Collins his office had been doing everything possible to account for citizens after the attack that killed 12 and injured almost 50 when a large truck was driven through a bustling Christmas market.
"We're actively in contact through social media and the various other networks we have," Mr Collins said.
"Throughout the evening eyesterday (in the aftermath of the attack), we were actively seeking to reassure ourselves that there were no Irish involved.
"Thankfully so far we have no information that any Irish citizen has been affected."
The Taoiseach has condemned the Berlin attack, saying acts of violence have no place in society.
Minister for Foreign Affairs Charlie Flanagan is urging Irish citizens in the city to make contact with their families, while anyone here worried about Irish people in Berlin can call his Department on 01 - 4082000.
Meanwhile, Enda Kenny has also condemned the murder of Russia's Ambassador to Turkey, and the attack on worshippers at an Islamic centre in Switzerland's largest city Zurich which left three people injured.
Update 11.55am: The Tánaiste Frances Fitzgerald has described as "unspeakably evil" the suspected terrorist attack in Berlin last night.
The Tánaiste said: "This appears to have been an attack not just on people innocently going about their business preparing for Christmas, but on freedom itself.
"Our values of democracy and liberty are the target of those who wish to see a world of dark tyranny imposed on us all.
"I know particularly from my international Ministerial counterparts that there is a steady determination to continue to take - and where possible enhance - measures to counteract this threat. And An Garda Siochana will continue to work closely with their international colleagues to this end.
"Ultimately the values we cherish so deeply will prevail."