Iran’s supreme leader and representatives of Palestinian militias he backs prayed Thursday over the coffins of Hamas leader Ismail Haniyeh and his bodyguard who were killed in a shocking assassination blamed on Israel that risked escalating into an all-out regional war.

Ayatollah Ali Khamenei prayed over Haniyeh’s coffin at Tehran University while Iran’s new President Masoud Pezeshkian stood next to him.

State television later showed the coffins placed in a truck and moved on the street toward Azadi Square in Tehran and people throwing flowers at them.

After the funeral services in Tehran, Haniyeh’s remains are to be transferred to Qatar for burial Friday.

Haniyeh came to Tehran to attend the inauguration of Pezeshkian.

Associated Press photos showed the Hamas leader seated alongside leaders from the Palestinian Islamic Jihad militant group and Hezbollah, and Iranian media showed him and Pezeshkian hugging.

Haniyeh had met earlier with Khamenei.

Hours later, he was killed in an airstrike that hit a residence Haniyeh uses in Tehran.

Iranian authorities said the attack is under investigation but haven’t provided details.

Israel had pledged to kill Haniyeh and other Hamas leaders over the group’s Oct. 7 attack on southern Israel that sparked the war in Gaza.

The strike came just hours after Israel targeted a top commander in Iran’s ally Hezbollah in the Lebanese capital Beirut.

Iran supports Hamas, as well as Hezbollah and other Palestinian militant groups fighting Israel in Gaza.

US Secretary of State Antony Blinken said “all parties” in the Middle East must avoid escalatory actions that could plunge the region into further conflict.

Speaking in the Mongolian capital of Ulaanbaatar on Thursday, Blinken appealed for countries to “make the right choices in the days ahead” and said a cease-fire between Israel and Hamas in Gaza was the only way to begin to break the current cycle of violence and suffering. Blinken did not mention Israel, Iran or Hamas by name in his comments.

Bitter regional rivals, Israel and Iran risked plunging into war earlier this year when Israel hit Iran’s embassy in Damascus in April.

Iran retaliated, and Israel countered in an unprecedented exchange of strikes on each other’s soil, but international efforts succeeded in containing that cycle before it spun out of control.

During Pezeshkian’s inauguration ceremony, in his speech, he spoke in support of Palestinians, saying “Iran demands a world where no Palestinian child’s dreams are buried under the rubble of their home.”

“We are seeking a world where the proud people of Palestine are freed from occupation, oppression and imprisonment and genocide,” Pezeshkian said.