The Tánaiste and Foreign Affairs Minister says the International Criminal Court must investigate last night's explosion at a hospital in Gaza that's killed at least 500 people.
Hamas says it was an Israeli airstrike but Israel's military insists it has evidence to show it was another group Islamic Jihad which denies responsibility.
The US President has just arrived in Tel Aviv, where he will meet Israeli prime minister Benjamin Netanyahu and show his support following the Hamas attacks.
His meeting with the Palestinian president Mahmoud Abbas in Jordan has been cancelled following the explosion in Gaza.
Tánaiste Micheál Martin says the images emerging from Gaza are horrific.
'I condemn unreservedly the attack on this hospital and I do believe that the international criminal court, which has jurisdiction over Israel and the occupied territories should investigate this.'