Iran's supreme leader vowed retaliation on Saturday for attacks by Israel, as an Israeli military official confirmed naval commandos seized a suspected Hezbollah operative in a Lebanon raid.
The World Health Organization said four children were among six people wounded in a strike on a polio vaccination centre in north Gaza, where UN agencies have spoken of "apocalyptic" conditions in the face of a blistering Israeli assault.
Days before the presidential election in the United States -- Israel's main military supplier -- Ayatollah Ali Khamenei said Iran's response would cover attacks on both the Islamic republic and its allies.
"The enemies, both the USA and the Zionist regime, should know that they will definitely receive a tooth-breaking response," Khamenei said, referring to Iran-aligned groups including those in Yemen and Syria.
On October 26, Israel bombed military sites in Iran, killing four servicemen, in response to an October 1 barrage of about 200 missiles that Tehran called a reprisal.
Israel has warned Iran against responding to the October 26 attack.
Analysts say Israel inflicted severe damage on Iranian air defences and missile capacities and could yet launch more wide-scale action against the Islamic republic.
The US military said Saturday its B-52 bombers have arrived in the Middle East, a day after Washington announced their deployment in a warning to Tehran.
- Gaza 'darkest periods' -
Since late September Israel has been engaged in full-scale war against Iran-backed Hezbollah in Lebanon while fighting continues against the Palestinian militant group Hamas, which triggered the Gaza war by attacking Israel on October 7 last year.
Israeli forces have carried out a major air and ground assault since October 6 in north Gaza, centred on the Jabalia area, vowing to stop Hamas from regrouping.
WHO chief Tedros Adhanom Ghebreyesus said the agency had received "an extremely concerning report" about a strike on the Sheikh Radwan health centre.
The facility "was struck today while parents were bringing their children to the life-saving polio vaccination" drive, he said.
Tedros did not specify who carried out the strike, but a source in Gaza's civil defence agency told AFP that it was "an Israeli quadcopter that fired two missiles which hit the wall of Sheikh Radwan clinic".
The Israeli military denied striking near the clinic at the time.
The UN children's agency said "the attacks on Jabalia, the vaccination clinic and the UNICEF staff member are yet further examples of the grave consequences of the indiscriminate strikes on civilians in the Gaza Strip."
UNICEF chief Catherine Russell said 50 children had been reported killed over 48 hours in Jabalia.
"Taken alongside the horrific level of child deaths in North Gaza from other attacks, these most recent events combine to write yet another dark chapter in one of the darkest periods of this terrible war," she said in a Saturday statement.
Israel's military said dozens of militants were killed around Jabalia "in aerial and ground activity".
Two rockets were fired into Israel from the area on Saturday, the military said, the first such attack in weeks.
Medics and Gaza's civil defence agency reported three people killed in a strike on Nuseirat, in central Gaza.
"We came out and there were planes and gunfire above us," said Ashraf Abdullah, describing the victims as "all torn to pieces".
Hamas's October 7, 2023 attack on southern Israel resulted in the deaths of 1,206 people, mostly civilians, according to an AFP tally of Israeli official figures.
Israel's retaliatory military campaign has killed 43,314 people in Gaza, most of them civilians, according to figures from the Hamas-run territory's health ministry which the UN considers reliable.
The Israeli military said two soldiers were killed in Gaza on Saturday, bringing its losses to 370 since the start of the ground offensive on October 27 last year.
- No heating, warm clothes -
After nearly a year of tit-for-tat exchanges across Israel's northern border, Israel escalated its bombing campaign against Hezbollah targets in Lebanon on September 23 and later sent in ground troops.
Hezbollah has since fired more deeply into Israel.
On Friday, Israeli naval commandos seized a trainee mariner a military official described as a "senior operative" of Hezbollah in a raid in northern Lebanon and brought him to Israel.
Lebanese Prime Minister Najib Mikati instructed the foreign ministry to submit a complaint to the UN Security Council over the raid in coastal town of Batroun, his office said.
The Lebanese military and UN peacekeeping force UNIFIL are both conducting investigations into the raid, Mikati's office said, adding that he had called for "expedited" results.
Lebanon's state-run National News Agency said an "unidentified military force" carried out a "sea landing" on the shore of Batroun at dawn Friday.
An acquaintance of the abductee identified him as a student at the city's state-run Maritime Sciences and Technology Institute (MARSATI), Lebanon's primary training college for the shipping industry.
Israel's broader strikes across Lebanon have displaced hundreds of thousands of people.
"There's no heating. We don't have warm clothes," said Fatima, 17, who now camps out with her family at a school near Deir al-Ahmar, in Lebanon's eastern Baalbek area.
The bombardment has killed at least 1,930 people in Lebanon since the war escalated, according to an AFP tally of health ministry figures.
Israel's military says 38 soldiers have been killed in Lebanon since it began ground operations on September 30.
Israeli strikes against Hezbollah's south Beirut stronghold on Saturday killed one person and wounded 15, the health ministry said.