While visiting Kyiv, the taoiseach (Irish prime Minister) witnessed the destruction caused by the Russian invasion.
On Wednesday, Micheal Martin arrived at the Ukrainian capital. He was taken to the war-torn areas of Borodyanka or Irpin.
He also visited Bucha's mass grave.
Martin uses the visit to reaffirm Irish solidarity with Ukraine against Russian aggression.
The daylong itinerary began with a visit to Borodyanka, a small town near Kyiv that was heavily damaged by Russian shelling.
Martin met with the mayor of the town and saw apartment blocks that were destroyed by fire in the Russian bombardment.
There, Martin visited Bucha's mass grave, which was captured by the Russian forces in the early stages of the war.
The site was shown to Martin by a cleric, who showed him graphic photos of exhumed bodies as well as pictures of civilians killed in the streets after the Russian forces had fled.
The Irish delegation then traveled to Irpin, where they were shown the badly damaged apartment blocks that had been struck by Russian shells.
After the attack, Martin stated that it was difficult to understand the inhumanity and devastation caused by Russia's attacks against Irpin, Borodyanka, and Bucha.
"Remember how crucial it is for children and women to travel to Ireland to escape violence and trauma. We stand with Ukraine."
Later on Wednesday, Martin will be discussing how Ireland and EU can help Ukraine in meetings.
Martin will reiterate Ireland's support for continued sanctions against Russian President Vladimir Putin's government, in order to help Ukraine on its path to full EU membership.
He stated that the people of Ireland stood with Ukraine and its people against Russia's unprovoked and immoral war of terror.
"The attacks and bombardment of civilians is nothing less than war crimes. I will use my visit in Ireland to support efforts to hold those responsible for these attacks accountable."
"The spirit, determination, and will of the Ukrainian people have inspired us all. Ireland will provide every support to Ukraine on its path to full EU membership and continue to support civilians fleeing war.
Two weeks ago, President Volodymyr Zilensky invited Mr Martin to visit Ukraine.
It marks the first time a taoiseach has visited an eastern European country.
Martin warned that Russia's president was using its natural gas reserves to put maximum pressure on Europe in the lead up to the winter period.
The taoiseach was also a vocal advocate for Ukraine's rapid-tracked EU membership.
Before, Mr Zelensky thanked Ireland for its "active support" of Ukraine's European aspirations.
Since Russia invaded Ukraine at the beginning of February, more than 36,000 Ukrainians have been taken in by the Republic of Ireland.
The state provided 20m euros (PS17.1m), in humanitarian assistance and assistance to the country. It also donated more than 4.5m euros (PS3.8m) in health equipment and medical donations.