Tehran, 1 August 2024 (dpa/MIA) — Iran and its allies said Israel will face harsh retaliation for the assassination of Hamas leader Ismail Haniyeh in Tehran, a brazen attack that dramatically ratchets up tensions in a region already on edge.

"The criminal Zionist regime [Israel] has murdered our guest in our house," Iranian Supreme Leader Ayatollah Ali Khamenei said. "There will be a severe punishment."

Haniyeh had led Hamas' political operations for years. He was based in Qatar rather than in Gaza, where Israel's military has been waging a war to completely eliminate the Palestinian militant group since October.

UN Security Council calls for de-escalation

The UN Security Council on Wednesday convened in New York for an emergency session, requested by Iran and backed by China, Russia and Algeria, to discuss the escalation in the region.

"The international community must work together to prevent any actions that could make the conflict much bigger and wider very quickly," Rosemary DiCarlo, UN under-secretary-general for political affairs, said.

"Communication by means of missiles, armed drones and other deadly attacks must end," DiCarlo said.

The 15 council members all called for a de-escalation of the situation.

UN Secretary General António Guterres warned the latest incidents were a "dangerous escalation" and undermined the goal of ending the Gaza war, he said in New York.

"The secretary general urges all to vigorously work towards regional de-escalation in the interest of long-term peace and stability for all."

All actions that "could push the entire Middle East over the edge, with a devastating impact on civilians" must be avoided, he added.

US says escalation isn't inevitable

US National Security Council adviser John Kirby played down the risks of an increase in hostilities.

"We don't believe that an escalation is inevitable, and there's no signs that an escalation is imminent. But I also said that we watch it very, very closely," Kirby said.

"It was always complicated. It remains complicated and and reports coming out of the region, as we've seen again, over the last 24 to 48 hours certainly don't make it less complicated."

Netanyahu says Israel prepared for every scenario

Israel's military has not commented on Haniyeh's assassination, although Israeli politicians have welcomed his death.

Israeli Prime Minister Benjamin Netanyahu told citizens in Israel to be ready for "challenging days" ahead.

"We are prepared for every scenario and will stand united against all threats," Netanyahu said after a meeting of the Israeli security cabinet at military headquarters in Tel Aviv.

"Israel will exact a high price for any aggression against us, from any front," he said.

"Since the beginning of the war, I have declared that we are fighting against the Iranian axis of evil," Netanyahu said in his televised address.

"This is a fight for survival against a ring of terrorist armies and missiles that Iran wants to tighten around our necks."

The main players are Hamas, Hezbollah and the Houthis in Yemen, he said. Israel has recently dealt hard blows to all three players.

"We will settle the score with anyone who harms us," the premier said.

Haniyeh's death was second high-profile assassination

Iran's Islamic Revolutionary Guard Corps and Hamas confirmed that Haniyeh was killed at a residence he was staying at in Tehran. The attack took place hours after he attended an inauguration ceremony in parliament for new Iranian President Masoud Pezeshkian.

"A rocket hit the room where Ismail Haniyeh was staying and he was hit directly," said senior Hamas official Khalil al-Haja at a press conference in Beirut.

Haniyeh's death was the second high-profile assassination in the span of around 12 hours. Israel says it killed a top Hezbollah commander, Fuad Shukr, in Beirut on Tuesday.

The Hezbollah militant group in southern Israel has deep ties with Hamas, and both are backed by Iran.

Israel's foes express outrage at killing

Israel's foes expressed outrage at Haniyeh's killing and demanded retribution.

The al-Qassam Brigades, the military wing of Hamas, said Israel "will pay the price for its aggression."

Netanyahu is "blinded by megalomania" and is leading Israel "towards the abyss and is speeding up its collapse and disappearance from the land of Palestine once and for all," a statement said.

The terrorist group Palestinian Islamic Jihad, which is active in Gaza, described Haniyeh as a "symbol of resistance," while the Houthi militia in Yemen called his death "a great loss."

The Houthi militia stands firmly alongside Hamas, with both groups supported by Iran.

The Turkish Foreign Ministry has called the killing "despicable attack" and accused Israel of wanting to expand the war against Hamas in Gaza to the entire region.

Hezbollah said Haniyeh's death "will increase the resistance fighters' determination ... to continue the path of jihad," using an Arabic word meaning 'holy war' or 'internal struggle against sin.'

China also condemned the killing and called once again for a ceasefire in the region.

Funeral details announced

Haniyeh will be buried in Qatar following funeral prayers on Friday.

A public and official funeral service will be held on Thursday in Tehran, where Haniyeh was killed. After that, the body will be transferred to the Qatari capital, Doha.

Funeral prayers will be held on Friday in Doha, then he will be laid to rest at a cemetery in Lusail, north of the capital.

Iran issued a statement also blaming the United States for his death in addition to Israel.

"The US is also responsible for this brutal act of terrorism," a Foreign Ministry statement said.

Washington had always supported the Israeli government and consistently endorsed its crimes, thus also playing a role in this incident, it added.

US Secretary of State Antony Blinken said on Wednesday that Washington was not involved in the Haniyeh's assassination.