Israel on Saturday again carried out deadly air strikes on north Gaza, where the UN calls conditions "apocalyptic", as Israel continues its deadly assault on Lebanon.
Since late September Israel has been engaged in full-scale war on Lebanon while it continues its devastating war on Gaza.
The war has threatened to spiral even further after Israel initiated tit-for-tat strikes with Iran over the past few months. Iran's supreme leader vowed on Saturday a further response to attacks against the Islamic republic and its allies.
Since 6 October Israeli forces have carried out a major air and ground assault on north Gaza, centred on the Jabalia area, destroying what remains of the camp and blocking aid into it.
"The situation unfolding in north Gaza is apocalyptic," said a joint statement by UN agency heads."The area has been under siege for almost a month, denied basic aid and life-saving supplies while bombardment and other attacks continue," the heads of the humanitarian, health and other agencies said.
"The entire Palestinian population in North Gaza is at imminent risk of dying from disease, famine and violence."
Witnesses said Israeli warplanes twice hit Beit Lahia, adjacent to Jabalia, overnight.
Israel's military on Saturday said dozens of militants were killed around Jabalia "in aerial and ground activity."
Troops were also operating in central Gaza and Rafah in the territory's far south, it added, while witnesses said Israeli drones and boats opened fire on Al-Mawasi in south Gaza.
Medics and Gaza's civil defence rescuers on Saturday reported three people killed in a strike on Nuseirat, in central Gaza, a day after AFP images showed the blood-stained shrouds of several people killed there in an Israeli strike.
After nearly a year of tit-for-tat exchanges over Israel's northern border, which Hezbollah said were in support of Hamas, Israel on September 23 escalated its bombing campaign against targets in Lebanon and later sent in ground troops.
Hezbollah has since fired more deeply into Israel.
A strike in Israel's Sharon area north of Tel Aviv wounded 19 people, police said early Saturday, after the army reported three projectiles fired from Lebanon into central Israel.
Four of the wounded were "in moderate condition", the Israeli police said.
Hezbollah said it had again launched rockets at Israel's Glilot intelligence base near Tel Aviv.
Late Friday, Lebanon's health ministry said 52 people had been killed in Israeli strikes in the country's east, attacks for which the Israeli army had not issued evacuation warnings.
Since the war escalated Israeli strikes have killed at least 1,911 people in Lebanon, according to an AFP tally of health ministry figures.
Israel's military says 37 soldiers have been killed in Lebanon since it began ground operations on 30 September.
According to Israeli figures, at least 63 people have been killed on the Israeli side since October last year.
Fears the war could engulf the entire Middle East intensified with tit-for-tat exchanges between Israel and Iran.
On 26 October, Israel bombed military targets in Iran, killing four servicemen, in retaliation for the Islamic republic's barrage of around 200 missiles against Israel on 1. Iran had said that barrage was itself a reprisal for the killing of top militants and a general in the Revolutionary Guards.
"The enemies, both the USA and the Zionist regime, should know that they will definitely receive a tooth-breaking response to what they are doing against Iran, the Iranian nation, and the resistance front," supreme leader Ayatollah Ali Khamenei said.
He was referring to Iran-aligned groups which also include those in Yemen, Iraq and Syria.
Analysts say Israel inflicted severe damage on Iranian air defences and missile capacities and could yet launch more wide-scale action against Iran.
On Saturday the Israeli military said it had intercepted three drones over the Red Sea, after late Friday reporting seven drones had been launched from "several fronts".
Israel's war on Gaza has killed 43,259 Palestinians, most of them civilians, and thousands of whom are women and children.