Israel's army said it had killed the cleric tipped to succeed slain Hezbollah leader Hassan Nasrallah in an air strike on Beirut three weeks ago that targeted commanders of the Iran-backed militant group.

Hezbollah has not issued a statement about the Israeli claims to have killed Hashem Safieddine.

"It can now be confirmed that in an attack approximately three weeks ago, Hashem Safieddine, the head of Hezbollah's Executive Council, and Ali Hussein Hazima, the head of Hezbollah's Intelligence Directorate, were killed along with other Hezbollah commanders," the Israeli army said in a statement Tuesday.

The army said the air force had hit Hezbollah's main intelligence headquarters in the southern Beirut suburb of Dahiyeh, Hezbollah's stronghold in the Lebanese capital, and that more than 25 Hezbollah militants were present at the time.

Longtime Hezbollah leader Nasrallah was killed on September 27 in an Israeli air strike on Beirut's southern suburbs.

Safieddine, tipped to succeed his distant cousin as leader of the Lebanon-based group, had been out of contact since Israeli strikes on Beirut weeks ago, a high-level Hezbollah source said at the time.

"We have reached Nasrallah, his replacement and most of Hezbollah's senior leadership", Israeli army chief Lieutenant General Herzi Halevi said in a statement after the confirmation of Safieddine's death.

After nearly a year of war with the Palestinian Islamist movement Hamas in Gaza, Israel shifted its focus to Lebanon in late September, vowing to secure its northern border threatened by cross-border fire from Hamas's Lebanese ally.

Israel ramped up its air strikes on Hezbollah strongholds around the country and sent in ground troops late last month, in a war that has killed at least 1,552 people since September 23, according to an AFP tally of Lebanese health ministry figures.

- Blinken presses for Gaza aid -

Israel's announcement of the death of Safieddine came as US Secretary of State Antony Blinken urged Prime Minister Benjamin Netanyahu to seize on the killing of Hamas leader Yahya Sinwar in Gaza last week to work towards a ceasefire in the Palestinian territory.

Blinken is on his 11th trip to the Middle East since Hamas's October 2023 attack on Israel triggered the Gaza war, and his first since Israel's conflict with Hezbollah escalated in late September.

During his meeting with Netanyahu in Jerusalem, Blinken "underscored the need to capitalise" on the death of Sinwar, US State Department spokesman Matthew Miller said.

This would be done by "securing the release of all hostages and ending the conflict in Gaza in a way that provides lasting security for Israelis and Palestinians alike", he added.

Netanyahu told Blinken that Sinwar's death "could have a positive impact on the return of the hostages" seized by Hamas during the October 7 attack last year, according to a statement from the Israeli leader's office.

Blinken also pressed for more aid to be allowed into besieged Gaza as concerns rise for tens of thousands of civilians trapped by fighting in the hard-to-reach north.

Blinken later met with Defence Minister Yoav Gallant who said they discussed the army's "achievements in its mission to destroy Hezbollah's attack infrastructure". 

In a post on X, Gallant said he had "emphasized the importance of standing together against Iranian aggression -- amplifying deterrence across the region".

Gallant told Blinken Israel expects Washington's support "following our attack on Iran", his office said earlier.

Israel is weighing its response to Iran's October 1 missile attack, which Tehran launched in retaliation for the killing of Nasrallah in Beirut and of Hamas leader Ismail Haniyeh in Tehran in July.

Previous US efforts to end the Gaza war and contain the regional fallout have failed, as did a bid spearheaded by President Joe Biden and his French counterpart Emmanuel Macron to secure a temporary ceasefire in Lebanon.

After Israel, Blinken will visit Saudi Arabia on Wednesday, a US official said.

- South Beirut evacuation orders -

Fighting meanwhile raged in Lebanon, with the Israeli military again striking the southern suburbs of Beirut Tuesday evening, after issuing new calls for residents to evacuate the area.

On Tuesday, an Israeli strike on the eastern Hermel region killed five people, while five more died from a separate strike in the southern city of Nabatiyeh, the Lebanese health ministry said.

An Israeli air strike near a Beirut hospital killed 18 people, four of them children, according to the ministry.

The strike flattened four buildings near the Rafic Hariri Hospital, Lebanon's biggest public health facility which is outside Hezbollah's traditional strongholds, an AFP correspondent reported.

Resident Ola Eid said she was tossing children chocolate and candy from her balcony when her neighbourhood was bombed.

"Before they could even catch them, the first strike hit, then a second. I saw the children ripped apart," she told AFP.

UN human rights chief Volker Turk said he was "appalled" by the strike.

Hezbollah also continued to fire into Israel through Tuesday, launching about 140 "projectiles" from Lebanon, the Israeli military said.

- 'Bodies lying on the streets' -

In the Gaza Strip, Israel launched a major air and ground assault in northern Gaza this month, vowing to stop Hamas militants from regrouping in the area.

Despite the exodus of tens of thousands of civilians, around 400,000 have been trapped by the fighting, the UN agency for Palestinian refugees warned last week.

The only medical facility still partially functioning in the targeted area of northern Gaza has "no medicine or medical supplies", warned Kamal Adwan Hospital director Hossam Abu Safia.

"People are being killed in the streets, and we can't help them. Bodies are lying on the streets."

The war was sparked by Hamas's unprecedented attack on Israel on October 7 last year, which resulted in the deaths of 1,206 people, mostly civilians, according to an AFP tally of Israeli official figures.

Israel's retaliatory offensive has killed 42,718 people in Gaza, also mostly civilians, according to figures from the Hamas-run territory's health ministry which the UN considers reliable.