An Taoiseach Micheál Martin has arrived in the Ukrainian capital Kyiv to meet President Volodymyr Zelenskyy.
It is the first ever visit to Ukraine by an Irish Taoiseach.
Mr Martin will become the latest in a string of world leaders to visit Ukraine, after an overnight journey by land.
The Government says Mr Martin is there to express the Irish people's solidarity "in the face of Russia's illegal and immoral war on Ukraine."
On the visit, he will engage with Ukrainian authorities on how Ireland and the EU can support the country’s current and future needs.
He will also witness first-hand the devastation caused by the bombardment and targeted attacks on civilians during the invasion and occupation by Russian forces.
Mr Martin will reiterate Ireland's full backing for continuing sanctions against Putin's regime, and for Ukraine's path to full EU membership.
He will also talk about Ireland's commitment to work with the European Union to ensure the reconstruction of Ukraine.
Speaking ahead of his visit, he said: "The people of Ireland stand with Ukraine and its people in the face of Russia's immoral and unprovoked war of terror.
"The bombardment and attacks on civilians are nothing short of war crimes, and I will use my visit to express Ireland’s support for moves to hold those behind these attacks fully accountable.
"The spirit and resolve of the Ukrainian people has inspired us all, and Ireland will provide every support for Ukraine's path to full EU membership, and continue to welcome and support civilians fleeing this war."