The World Health Organization chief warned Saturday of a disastrous situation in the north of war-ravaged Gaza, with "intensive military operations unfolding around and within healthcare facilities".

"The situation in northern Gaza is catastrophic," Tedros Adhanom Ghebreyesus said on X, warning that "a critical shortage of medical supplies, compounded by severely limited access, are depriving people of life saving care."

He highlighted Kamal Adwan, northern Gaza's last functioning hospital, which was stormed by Israeli forces on Friday, according to Gaza's health ministry.

Iran warned on Saturday it would defend itself after Israeli air strikes killed at least four soldiers and further stoked fears of a full-scale war in the Middle East.

Israel warned Iran would "pay a heavy price" if it responded to the strikes, and the United States, Germany and Britain demanded Tehran not escalate the conflict further.

US President Joe Biden said he hoped "this is the end" after the pre-dawn Israeli strikes, noting that "it looks like they didn't hit anything other than military targets".

At least 50 people have been killed in a single attack by Sudanese paramilitaries who have besieged and raided villages in al-Jazira state, activists said.

The paramilitary Rapid Support Forces (RSF) have been at war with Sudan's regular army since April 2023 but have in recent days intensified their violence against civilians in al-Jazira, south of the capital Khartoum, after their commander in the state defected to the army.

Residents of Tehran awoke and went about their business as planned on Saturday after their sleep was troubled by Israeli strikes that triggered blasts that echoed across the city.

The night skies had been criss-crossed by light trails from air defence weapons, but by mid-morning the capital had resumed its usual rhythm and buses wove through the streets, taking troubled Iranians to work.

Iranian officials and media have played down the attack, but on the streets of Tehran many were concerned that it had marked a new escalation and a step towards all-out war.

Lebanese state media said the Israeli army dynamited houses in Lebanese border villages on Saturday, as Israel said it used 400 tonnes of explosives to destroy a Hezbollah tunnel, more than a month into an all-out war.

The official National News Agency said "the army of the Israeli enemy has since dawn blown up and destroyed houses" in the border village of Adaisseh.

The NNA also reported "large explosions" in the border village of Kfar Kila, saying the blasts were heard across the south as columns of smoke rose above the area.

Iran said Israeli air strikes targeting its military sites killed two soldiers on Saturday, after Israel said its warplanes carried out raids in retaliation for a missile barrage.

Here's what we know:

- What happened? -

The Israeli army said it conducted "precise strikes on military targets in Iran" on Saturday.

Explosions were heard in Tehran from around 2:15 am, AFP journalists in the Iranian capital said.

Iranian state television said the blasts were caused by the "activation of the air defence system" in response to an Israeli attack.

Iran said an Israeli attack targeted military sites in the Islamic republic on Saturday, killing two soldiers, almost a month after Israel vowed to avenge a missile barrage that raised fears of a full-scale Middle East war.

The Israeli military said its retaliatory air strikes hit Iran's missile manufacturing facilities, missile installations and other systems in several regions. It warned Iran it would "pay a heavy price" if it responded.

Swedish climate activist Greta Thunberg on Friday visited Istanbul's Acik Radyo, whose broadcasts were silenced earlier this month by Turkish authorities after a guest spoke on air about the "Armenian genocide", the station said.

"Greta supports Acik Radyo," it wrote on X, posting a video of the 21-year-old activist expressing support for the broadcaster whose name means "open radio".

Israel raids have left wrecked roads, bullet-riddled buildings and debris-strewn streets in the occupied West Bank city of Jenin, preventing ambulances from reaching those in desperate need of care.

"It is not only difficult, but also unsafe to reach the hospital during clashes," said Wissam Baker, the director of Jenin's hospital.

Patients needing dialysis, chemotherapy or maternity care are particularly vulnerable, he said, as delays in treatment could be life-threatening.

Yet their lives are also at risk when trying to get treatment.

Seeking a safe place to rest while covering the war in Lebanon, a group of journalists had gone to sleep in an area outside Hezbollah control, only to be awoken Friday by a deadly Israeli air strike.

The strike on Hasbaya at around 03:30 AM (1230 GMT) killed cameraman Ghassan Najjar and broadcast engineer Mohammad Reda, who worked for the pro-Iran, Beirut-based broadcaster Al Mayadeen, and video journalist Wissam Qassem of Hezbollah's al-Manar television.