Explosions in secretive underground nuclear facilities. Cyber attacks. Top scientists poisoned. Natural gas pipelines sabotaged. All these and more have been blamed on Israel in its shadow war with Iran.

And the latest accusation, that Israel is behind the assassination of Hamas leader Ismail Haniyeh in Tehran, only expands that list.

The leader of Yemen’s Houthi rebels said Thursday that efforts were underway to militarily respond to Israel following the killings of senior Hamas and Hezbollah leaders that have raised the prospect of war in the region.

The leader of the militant group, Abdul-Malek al-Houthi, said in a televised speech that “there must be a military response to the serious crimes and the significant escalation by the Israeli enemy.” “Efforts are underway to respond,” he added.

U.S. President Joe Biden has told Prime Minister Benjamin Netanyahu that Washington is committed to defending Israel's security "against all threats from Iran," the White House said, after the assassination of a top Hamas leader in Tehran.

Biden, who was joined on the call by Vice President and Democratic presidential candidate Kamala Harris, also emphasized the "ongoing efforts to de-escalate broader tensions in the region," the White House said Thursday in a statement.

Mourners arrived at a Qatari mosque on Friday to farewell Hamas leader Ismail Haniyeh after his killing in Tehran, an attack blamed on Israel that deepened fears of wider war.

Haniyeh, the Palestinian armed group's political chief, played a key role in mediated talks aiming to end nearly 10 months of war between his Islamist movement and Israel in Gaza.

Prime Minister Benjamin Netanyahu said on Thursday that Israel was prepared for any "aggression" against it following threats of retaliation for the killings of top Hamas and Hezbollah figures.

"Israel is at a very high level of preparation for any scenario, both defensive and offensive. We will make any act of aggression against us pay a very high price... Those who attack us, we will attack in return," Netanyahu said in a statement.

Iran and armed groups backed by it are preparing coordinated action meant to deter Israel but avert all-out war, sources and analysts said, after the killings of top Hamas and Hezbollah figures.

On Wednesday, Iranian officials met in Tehran with representatives of the so-called "axis of resistance" -- a loose alliance of Tehran-backed groups hostile to Israel -- to discuss retaliation for the deaths of Hamas's leader and Hezbollah's top military commander, said a source close to Lebanese group.

The Iran-aligned "axis of resistance" against Israel and its allies have lost two major figures in less than 24 hours in attacks either blamed on or claimed by Israel.

Hamas political chief Ismail Haniyeh was killed on Wednesday in Tehran in a strike the group blamed on Israel, hours after top Hezbollah commander Fouad Shukur perished in an Israeli strike on southern Beirut.

Ismail Haniyeh was the international face of Hamas, its top leader in exile who kept up the militant group's ties with allies around the region. At the head of its political hierarchy, he had little military role – but Israel marked him for death after the surprise Oct. 7 attacks.

The 62-year-old Haniyeh was killed in an airstrike Wednesday during a visit to one of Hamas' most crucial allies, Iran, after attending the inauguration of its new president. Iran and Hamas both accused Israel, which has not commented on the strike.

A pair of assassinations of anti-Israel militant leaders hours apart is threatening to set off a regional clash and upend already fragile talks aimed at ending the war in Gaza.

The deadly round of strikes, retaliation and negotiations escalated Wednesday when Hamas' political chief, Ismail Haniyeh, was killed, hours after he attended the inauguration of Iran's new president in Tehran. Israel has not claimed responsibility, but Iran threatened revenge against Israel.

Two Al-Jazeera reporters were killed in an Israeli strike in northern Gaza on Wednesday, the satellite news network said, the latest Palestinian journalists working with the Qatari network to be killed in the war-torn enclave.

Correspondent Ismail al-Ghoul, 27, cameraman Rami al-Rifi and a child who was not identified were killed in a blast that struck a car in Gaza City that the three were traveling in, according to the network and the Emergency and Ambulance Service, which helps recover and transport casualties to hospitals across Gaza.