Four senior officials at the Russian Embassy have been asked to leave the State, the Taoiseach has told the Dáil.
It follows security advice received by Micheál Martin yesterday.
The Russian Ambassador was summoned to a meeting in the Department of Foreign Affairs today.
The Government said the officials' activities have not been in accordance with international standards of diplomatic behaviour.
Speaking in the Dáil, Mr Martin said he believes that diplomatic channels should remain open. He was responding to a question from Labour Party leader Ivana Bacik.
Ms Bacik asked if the position of the Russian Ambassador "is now under threat", and urged his expulsion also.
There were 30 accredited officials working at the Russian Embassy in Ireland while just six officials are based at the Irish Embassy in Moscow.
Mr Martin said the expulsion of the four diplomats will send a signal expressing Ireland's abhorrence of the war in Ukraine.
He was responding to Sinn Féin leader Mary Lou MacDonald who asked who the officials are, and what they had done to warrant expulsion.
She said that the Government has been asked to expel the Ambassador along with all his staff.
A statement released on Twitter from the Russian Embassy said the decision to ask four of its diplomatic staff to leave Ireland is "groundless".
The statement said that the Embassy was informed of the decision today.
"The Embassy of Russia in Ireland has been informed by the Department of Foreign Affairs of Ireland of the decision by the Government of Ireland to request that four members of the diplomatic staff of the Embassy leave Ireland shortly, because allegedly their actions have been found to be unacceptable," said the statement.
It said it rejects "such qualifications" of the work of its diplomats.
The statement said the "arbitrary, groundless decision ... can only deteriorate further Russian-Irish relations, already damaged by the Irish participation in illegitimate EU sanctions against Russia".
"The Embassy proceeds from the assumption that such a step by the Irish side will not go unanswered," added the statement.
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The Taoiseach said Ireland worked with other countries on the expulsion but it was not possible to get agreement among all 27 EU States on the issue.
Belgium is expelling 21 Russian diplomats on suspicion of espionage, the country's foreign minister, Sophie Wilmes, said today.
Ms Wilmes, who made the announcement to parliament and on Twitter, said the move was coordinated with neighbouring Netherlands, which said it was expelling 17 Russian diplomats.
The four staff in Ireland were expelled under the 1961 Vienna Convention.
Article 9 of the Vienna Convention states: "The receiving State may at any time and without having to explain its decision, notify the sending State that the head of the mission or any member of the diplomatic staff of the mission is persona non grata or that any other member of the staff of the mission is not acceptable.
"In any such case, the sending State shall, as appropriate, either recall the person concerned or terminate his functions with the mission. A person may be declared non grata or not acceptable before arriving in the territory of the receiving State."
