Iran's supreme leader Ayatollah Ali Khamenei has vowed to retaliate against attacks by Israel and its ally the United States targeting Iran and groups it supports in the region.
"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," Mr Khamenei said in a speech to students in Tehran.
He was referring to the alliance of Tehran-backed armed groups that include Yemen's Houthi rebels, Lebanon's Hezbollah movement and the Palestinian Islamist group Hamas.
Regional tensions have soared since the outbreak in October last year of the Israel-Hamas war in Gaza, drawing in those Iran-aligned groups and others from Iraq and Syria.
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On 26 October, Israel conducted air strikes on military sites in Iran in response to Iran's 1 October attack on Israel, itself retaliation for the killing of Iran-backed militant leaders and a Revolutionary Guards commander.
At least four soldiers were killed in the attack which Iran said caused "limited damage" to a few radar systems. Iranian media said a civilian was also killed.
In his speech, Mr Khamenei paid tribute to the slain soldiers, saying their efforts in confronting Israel "will not be forgotten".
Israel has warned Iran against responding to the 26 October attack.
Mr Khamenei said Iran was "certainly doing everything that should be done to prepare the Iranian nation, whether in terms of military, in terms of weapons, or in terms of political work", without elaborating.
Revolutionary Guards spokesman Ali Mohammad Naini said Iran would respond "decisively" to Israel.
"The enemy should learn that it cannot commit any evil (it wants); it will undoubtedly receive a crushing response to its evildoing," said Mr Naini, the Fars news agency reported.
Further deadly Israeli air strikes on 'apocalyptic' north Gaza
It comes as Israel again carried out deadly air strikes on north Gaza, where the UN has described conditions as "apocalyptic", while Lebanon's Hezbollah has intensified rocket fire near Israel's commercial hub of Tel Aviv, on Israel's second front.
Since late September Israel has been engaged in full-scale war against Iran-backed Hezbollah in Lebanon while fighting continues against the Palestinian Islamist group Hamas, which triggered the Gaza war by attacking Israel on 7 October last year.
The war has threatened to spiral even further after Israel and Iran attacked each other over the past few months. Iran's supreme leader has vowed a further response to attacks against the Islamic republic and its allies.
Since 6 October this year Israeli forces have carried out a major air and ground assault on north Gaza, centred on the Jabalia area, vowing to stop attempts by Hamas militants from regrouping.
"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 has 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 have 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 23 September 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 this morning 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.
AFP images from Tira, a predominantly Arab town about 25km northeast of Tel Aviv, showed the upper wall blown out in what appeared to be a residential building.
Several cars below were crushed.
Israel's military said a strike around the southern Lebanese city of Tyre yesterday killed two fighters "responsible for firing over 400 projectiles at Israel over the last month alone".
Late yesterday, 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.
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