ReutersThousands of people attended the funeral of Hamas political leader Ismail Haniyeh, who was killed in an air strike in Tehran on Wednesday.
Iran’s Supreme Leader, Ayatollah Ali Khamenei, has led prayers for the Hamas leader, whose body will be buried in Qatar.
US media quoted Iranian officials as saying the supreme leader had ordered a direct attack on Israel, which they said was responsible for the attack on Iranian territory.
Israel has not commented directly on the assassination.
However, Israeli Prime Minister Benjamin Netanyahu said his country had dealt “crushing blows” to its enemies in recent days, including the assassination of a senior Hezbollah commander in Lebanon hours before the Tehran air strike.
He warned Israelis that “challenging days lie ahead”, as fears of a wider conflict in the Middle East grow.
“Since the attack in Beirut, we have heard threats from all sides,” he said in a televised address.
“We are prepared for all situations and will be united and determined.”
UN Secretary-General Antonio Guterres warned of a “dangerous escalation” of hostilities in the region.
The Hamas militant group said the death of Haniyeh, widely seen as the group’s overall leader, would “take the war to a new level” and have major consequences.
The group attacked Israel on October 7, killing some 1,200 people. Since the attack, Israel has vowed to destroy Hamas.
Haniyeh, who played a key role in Gaza ceasefire negotiations, was killed hours after attending the inauguration of Iran’s new president, Masoud Pezeshkian, in Tehran.
A senior Hamas official told the BBC the killing took place in the same building where Haniyeh had stayed on previous visits to Iran.
They said three Hamas leaders and several guards were with him in the building.
Khalil Al-Hayya, a senior Hamas official, quoted witnesses at the scene as saying at a news conference that a rocket had hit Haniyeh “directly”.
Senior Hamas officials told the BBC that the group’s leadership was in a “state of shock”.
Hours before Haniyeh was targeted, Israel said it had killed senior Hezbollah leader Fuad Shukr in Beirut.
Israel believes he was responsible for a rocket attack that killed 12 people in the Israeli-occupied Golan Heights on Saturday. Hezbollah has denied any involvement.
The Iran-backed group confirmed that Shukr’s body was found in the rubble of a residential building that was hit by a bomb. Four other people, including two children, were killed.
