Iran is promising “revenge” after Hamas leader Ismail Haniyeh was killed in Tehran.

Iranian Supreme Leader Ali Khamenei said after the assassination, “The criminal and terrorist Zionist regime martyred our dear guest in our home and made us sad, but it also prepared a harsh punishment for itself.”

“Martyr Haniyeh was willing to sacrifice his honorable life in this dignified battle for many years,” Khamenei continued.

He added, “He was prepared for martyrdom and had sacrificed his children and loved ones on this path. He was not afraid of being martyred on the path of God and in order to save the lives of God’s servants. However, following this bitter, tragic event which has taken place within the borders of the Islamic Republic, we believe it is our duty to take revenge.”

Hamas said the assassination “take the battle to new dimensions and have major repercussions.”

Haniyeh’s death came after he attended the swearing of Iran’s new president.

Reuters reports, “Haniyeh, normally based in Qatar, has been the face of Hamas’s international diplomacy as the war set off by the Hamas-led attack on Israel on Oct. 7 has raged in Gaza. He had been taking part in internationally-brokered talks on reaching a ceasefire in the Palestinian enclave.”‘

Qatar’s Prime Minister Sheikh Mohammed bin Abdulrahman Al Thani wrote on X to criticize the assassination, “Political assassinations and continued targeting of civilians in Gaza while talks continue leads us to ask, how can mediation succeed when one party assassinates the negotiator on other side?”

Israel has not claimed responsibility for the strike.

The assassination of Haniyeh came hours after Israel claimed to have killed a Hezbollah commander in Lebanon, who it said was behind a deadly strike in Israel over the weekend.