Taoiseach Micheál Martin is travelling to war-torn Ukraine to meet with President Volodymyr Zelensky.
It is understood that Mr Martin and his entourage will travel to Kyiv by train ahead of a series of engagements on Wednesday.
His visit follows an invitation issued by Ukrainian President Volodymyr Zelensky during a telephone conversation between the two around a fortnight ago ahead of last month's European Council meeting.
Mr Martin’s trip marks the first official visit of an Irish Taoiseach to Ukraine.
He was noticeably absent from the Dáil on Tuesday with Tánaiste Leo Varadkar standing in for the Taoiseach at Leaders’ Questions.
Opposition parties were informed this morning that Mr Martin would not be in the Dáil this week. Details of the trip have been kept under wraps for security reasons.
But sources told Independent.ie that Mr Martin was travelling to Ukraine on Tuesday night and will meet with Mr Zelensky as well as visit the Ukrainian Parliament in Kyiv.
Speaking after their phone call last month, Mr Zelensky said that he invited Mr Martin “to make the first visit to Ukraine in the history of bilateral relations”.
Mr Martin said at the time that he was keeping the invitation under review.
The Taoiseach's spokesperson could not be reached for comment, while there was no immediate response from the Government Press Office.
Fine Gael Senator Garret Ahearne said it is a “sign of solidarity” for the Taoiseach to travel to Ukraine.
"The scenes he will witness in Kyiv can be very distressing but I believe it will intensify his commitment towards Ukraine until they are victorious,” he said.
“We are entering a new stage of this war with potential food storages in Northern Africa, and Europe's resolve will be tested. Ireland can play a leading role in advocating for Ukraine during this difficult period ahead."
Sinn Féin spokesperson Pearse Doherty welcomed the Taoiseach’s visit to Ukraine.
“I think it’s important, we’ve seen seen other leaders, we’ve seen the Ceann Comhairle, we’ve seen the chair of the Seanad [visit Ukraine] and I think it’s important to mark solidarity with the people of Ukraine,” he said.