Enda Kenny has warned a Berlin-style terror attack could not be ruled out in Ireland.
The Taoiseach has written to Chancellor Angela Merkel to express sympathy over the killing of 12 people and injuring of 48 when a truck ploughed into crowds at a Christmas market in the German capital on Monday.
Asked whether Ireland could be similarly targeted, Mr Kenny said bigger security and police forces in other countries had failed to prevent the likes of the Berlin atrocity or the almost identical attack on Bastille Day in Nice.
"You can never rule anything out," he said.
"But we like to think that in this country people are vigilant, that we are careful and we will do everything we can to protect our citizens."
The Taoiseach added: "I would hope that nothing like that will happen here."
Both the Berlin and Nice outrages were claimed by the so-called 'Islamic State' group.
Mr Kenny said the Gardaí and Defence Forces are making every effort possible "to see that we are protected and that lives are protected in that regard".
Separately, he rejected calls from an imam to regulate Irish mosques in an attempt to thwart Muslims here being radicalised.
Shaykh Dr Umar Al-Qadri, chairman of the Irish Muslim Peace and Integration Council, was reported as saying the Government should set up a Muslim council to regulate how mosques are being run and the education they are providing.
However, Mr Kenny said Ireland enjoys freedom of religion and religious practices and he did not agree with the suggestion.
"Obviously, we respect the right of every religion to preach to its own followers and we expected that preaching to be in accordance with peaceful means and the religious beliefs that people have," he added.