Taoiseach Micheál Martin has described the situation in Ukraine as "serious" and said the Government is recommending citizens to avoid non-essential travel there.
Mr Martin said the Minister for Foreign Affairs Simon Coveney spoke to the Russian Ambassador and made it clear the Government is "very unhappy and does not welcome the development".
“It is a very serious situation and we would appeal for de-escalation of tensions in respect of the massing of thousands and thousands of Russian troops on the Ukrainian border,” he told the Dáil on Tuesday.
Mr Martin said there are “fundamental principles” at stake.
"Ireland wants a diplomatic resolution, not only to the current situation but to the illegal annexation of Crimea. That is the Irish position," he added.
“We’ve updated our travel advice we’re recommending that citizens avoid now non-essential travel to the Ukraine.”
Mr Martin said Ireland and its EU colleagues support “comprehensive sanctions” if an invasion does take place.
“I earnestly hope it doesn’t and if the de-escalation of the aggression could happen, I think the world would breathe a collective sigh of relief because the world is trying to come through Covid-19 and all its implications. Now, to go through another crisis, which could occur as a result of an invasion, I think would be very, very difficult for the world as a whole to deal with,” he said.
Minister for Foreign Affairs Simon Coveney conceded that any reciprocal economic sanctions leveled by Russia could lead to a spike in energy prices in Europe.
“This could be the first land war in Europe that we’ve seen for many decades. It could result in an enormous loss of life and of course extraordinary disruption right across the continent of Europe,” he said, calling for a further reliance on diplomacy and political dialogue to diffuse tensions.
"The EU is absolutely unified also in terms of the deterrent that we need to put in place to ensure that Russia thinks very deeply before they would invade Ukraine. Because should they do that I think the response from a sanctions perspective coming from the European Union would be very, very comprehensive, going way beyond anything we have done in recent times."
Earlier, the Minister of State for European Affairs, Thomas Byrne warned that he fears war is looming in Europe because of the threat of a Russian invasion in Ukraine.
“I think this is really a moment of great danger in Europe and I’m not sure that we’re fully apprised of the seriousness of the situation that there is war looming in Europe and I think it is extremely, extremely worrying.
"I think we're in a very precipitous situation. There have been diplomatic efforts going on for weeks and months now at this stage to try to prevent this. We support all efforts to try to stop this – this could be very dangerous if it happens," he told RTÉ radio's Today with Claire Byrne show.
Mr Byrne called on Irish citizens in Ukraine to register with the Irish embassy which opened in Kyiv last year.
“We’ve a lot of Irish citizens there, what we’re asking is that Irish citizens register with the embassy. In our experience in situations such as this – whatever number of Irish people we have registered, there’s multiples more who aren’t registered.
“I think it’s very important that they do in case of the outbreak of hostilities and we are advising people not to go to Ukraine at the moment on any non-essential business or travel.”
Senior officials in Brussels are all "extremely concerned, extremely worried" about the situation. "We are showing as a European Union 100 per cent full solidarity with Ukraine – they're entitled to the integrity of their sovereign area, they're entitled to set their own destiny as a country. We must support democracy there and we must support their rights as a sovereign state."
Unlike the US, European countries were not withdrawing personnel from diplomatic missions in Ukraine, added Mr Byrne.
“It’s very important that we continue to review the security situation in Ukraine, we’re doing that all the time, obviously the safety of people there is very important. But it’s also important that we show full solidarity with Ukraine and not simply walk away from that. I think we’ve done that consistently”.
When asked about Russian plans for naval trials off the south west coast of Ireland, Mr Byrne echoed the comment by the Minister for Foreign Affairs Simon Coveney to the Russian Ambassador: “Russia are not welcome here, this is very, very worrying, as to what they are doing.
“The difficulty we have is that they are entitled to do this under international law in our exclusive economic zone, once they give notification to the Irish Aviation authority they are in compliance with international law.”