Irish premier Micheal Martin has said the forced landing of a Ryanair flight in Belarus was a “state-sponsored coercive act”.
Mr Martin said it was “piracy in the skies” and reflects a growing authoritarianism across the world.
Belarus state media said the aircraft – which was travelling from Athens in Greece to Lithuanian capital Vilnius – was switched to Minsk following an alleged bomb threat.
Authorities in Minsk arrested activist and blogger Roman Protasevich.
“Certainly it was a state-sponsored coercive act,” Mr Martin said.
The Taoiseach said forcing the plane to land in Belarus to arrest the journalist was “unacceptable”.
“I think it reflects a growing authoritarianism across the world but also these authoritarian leaders taking premeditated decisions of this kind, and the European Council will meet later this evening and tomorrow, and we’ll have to respond very strongly,” he added.
“There has to be measures that respond to it firmly to an act of this kind, which put the crew and the passengers at risk, it put their safety at risk, this kind of behaviour it’s piracy in the skies and it’s just not acceptable.”
A statement from authorities in Belarus said they acted “legally” and claims that KGB secret service members were on board the plane were “baseless”.
But Mr Martin described the statement as “nonsense”.
“I think we all know what happened here and don’t be hiding behind the rules, or don’t be hiding behind excuses,” he added.
“You forced the plane down to arrest a journalist whose views you don’t agree with, and that is contrary to any sense of decency or democratic values.”
Earlier, Ireland’s foreign affairs minister Simon Coveney described it as “state-sponsored aviation piracy”.
Mr Coveney said EU leaders need to make clear decisions following the incident, which opposition groups described as a “hijacking” of a plane.
“This was effectively state-sponsored aviation piracy,” Mr Coveney told RTE.
“It was an Irish airline, a plane registered in Poland, full of EU nationals, travelling between two EU capitals, flying through Belarusian airspace, which would be absolutely normal.
“It was intercepted, there was a warning given to the pilots and crew that there was a security risk on board and then the plane was was escorted by a military jet to Minsk airport, which was not the closest airport.
“It was essentially diverted back into Belarus, although it was still in Belarusian airspace, and landed in Minsk.
“(The EU) needs to make some clear decisions that send a very strong signal to a regime in Belarus that has no democratic legitimacy and is behaving as a dictatorship, repressing their own people, expelling foreign journalists, silencing civil society and human rights defenders.”
Mr Coveney said the EU’s response has to be “clear, tough and happen quickly”, and that he supports the idea of closing Belarusian airspace.
“I certainly think that that would be a very strong response and in principle I have no issue with that,” he added.
“I think the sanctions need to be fully thought through in terms of consequences, but I think this is an incident that is on the upper end of the scale in terms of something that needs a very strong sanction-based response.
“We cannot allow this incident to pass on the basis of warnings or strong press releases.”
Mr Coveney said that while he did not know whether there were KGB officials travelling on the plane, he said five or six people got off and did not reboard after it landed.
Ryanair CEO Michael O’Leary described the incident as a “state-sponsored hijacking” and said it was a frightening experience for the crew and passengers.
“Unfortunately I can’t say much about it because the EU authorities and Nato are dealing with it at the moment,” he told Newstalk.
“We’re debriefing the crews, our crews did a phenomenal job to get that aircraft and almost all the passengers out of Minsk after six hours.
“We have to do a detailed debrief today with the Nato and EU authorities.
“I think it’s very frightening for the crew, for the passengers who were held under armed guard, had their bags searched.
“It was clear it appears that the intent of the Russian authorities was to remove a journalist and his travelling companion.
“We believe there was also some KGB agents offloaded from the aircraft as well.”
There has been widespread political condemnation from the US, Germany, Lithuania, Latvia, Estonia, Poland and the Czech Republic, with many calling for the suspension of all overflights.
Mr Protasevich was a co-founder of the Nexta TV channel which was declared extremist by the authorities last year after helping to organise mass demonstrations against Belarus President Alexander Lukashenko.
He subsequently fled to Poland and currently faces charges which could carry a prison sentence of up to 15 years.
Belarus state media said Mr Lukashenko personally ordered an MiG-29 fighter jet to escort the flight he was on to Minsk after a bomb threat was received while it was over Belarus territory.
Officials later said no explosives had been found on board while the deputy air force commander said the plane’s crew made the decision to land in the Belarus capital.