The Israel-Hamas war entered its 200th day on Tuesday with fears mounting of an Israeli invasion in the overcrowded south of the besieged Gaza Strip amid calls for hostages to be freed.

The Israeli army carried out intense shelling overnight of Gaza City, AFP correspondents and witnesses said, with the military saying it also struck Hamas positions in south Gaza.

Shelling and loud explosions were heard in southwest Gaza and the city of Khan Yunis in the south, while air strikes struck near the Bureij refugee camp and artillery fire hit the Nuseirat refugee camp.

The war erupted when Palestinian militants poured across the border with Israel on October 7 in an unprecedented Hamas-led attack that resulted in the deaths of 1,170 people, according to an AFP tally of Israeli official figures.

In retaliation, Israel launched a military offensive that has killed at least 34,183 people in Gaza, mostly women and children, according to the health ministry in the Hamas-run territory.

About 250 people were abducted during the Hamas attack. Israel estimates that 129 captives remain in Gaza, including 34 who the military says are dead.

German Foreign Minister Annalena Baerbock on Tuesday called for the captives' release.

"As long as the hostages are not free, we will not let up," she said on X. "Only when they are home will peace have a chance."

As diplomacy aimed at ending the war stalls, key mediator Qatar said Hamas's political leadership would stay in Doha "as long as their presence here... is useful and positive in this mediation effort", according to foreign ministry spokesperson Majed al-Ansari.

The Gulf state, which has hosted Hamas leaders since 2012, said last week it was reassessing its mediation role, fuelling speculation that the Palestinian group could be asked to leave.

- Passover 'pain' -

Gaza's Civil Defence agency said Monday that about 200 bodies were uncovered of people killed and buried by Israeli forces at the Nasser Hospital in Khan Yunis, which Israel has yet to comment on.

The United Nations rights office said it was "horrified" by the destruction at Nasser and Gaza City's Al-Shifa hospital, the territory's two largest medical facilities, which were both previously raided by Israeli forces.

Demanding an "independent" probe, UN rights chief Volker Turk noted the "special protection" awarded to hospitals under international law.

"The intentional killing of civilians, detainees and others who are hors de combat is a war crime," he said.

Also on Monday, as Jewish people marked the start of the holiday Passover, Israel's military intelligence chief, Major General Aharon Haliva, resigned after taking responsibility for failures leading to the October 7 attack.

Public pressure has mounted on the government of Israeli Prime Minister Benjamin Netanyahu to strike a deal that would secure the release of the remaining hostages.

At a rally near Netanyahu's home in the coastal town of Caesarea, protesters including relatives of hostages set fire to a symbolic table for Passover, also known in Hebrew as the "holiday of freedom".

Dalit Shtivi -- the mother of Idan Shtivi, who was kidnapped from a music festival near Gaza on October 7 -- said she was struggling to cope without her son during Passover.

"It's so hard. I cannot explain the pain. I cannot explain and think of celebrating without him," she said in a statement.

In a holiday message, Netanyahu has said Israel's "resolve remains unyielding to see all hostages back with their families".

- Fears for aid 'lifeline' -

Global opposition has mounted over the civilian toll of Israel's Gaza offensive which has turned vast areas into rubble and sparked fears of famine.

The United Nations says "multiple obstacles" continue to impede delivery of urgently needed aid for Gazans desperate for food, water, shelter and medicine.

But Netanyahu has vowed to press on with a planned offensive on Rafah, the town on the border with Egypt where most of Gaza's 2.4 million population has sheltered.

Citing Egyptian officials briefed on the Israeli plans, the Wall Street Journal said Israel was planning to move civilians from Rafah to nearby Khan Yunis.

The operation would last two to three weeks and be done in coordination with the United States, Egypt and other Arab countries including the United Arab Emirates, the Journal reported.

Israel would then send troops into Rafah gradually, targeting areas where Hamas's leaders are thought to be hiding, in a military operation that would last six weeks, it added.

Foreign ministers of the G7 group of developed economies have said they oppose a "full-scale military operation in Rafah" because of the "catastrophic consequences" for civilians, fears shared by many aid groups.

With Rafah also being the main entry point for humanitarian relief into Gaza, an Israeli invasion there "means cutting the aid system off from its lifeline", said Ahmed Bayram, media adviser for the Norwegian Refugee Council in the Middle East.

The war has triggered violence across the region, including near-daily cross-border exchanges between the Israeli army and Lebanon's Hezbollah, a Hamas ally.

The Iran-backed Lebanese group said it launched drone attacks on two northern Israeli army bases on Tuesday, in retaliation for a strike deep into Lebanon that killed a Hezbollah fighter Israel described as "significant".

Hezbollah announced "a combined air attack using decoy and explosive drones", though Israel said it had "successfully intercepted" the strike.

The US Senate meanwhile is set to vote Tuesday on an aid package for its allies, including Israel, that is expected to land on President Joe Biden's desk by the end of the week.

It earmarks $13 billion for Israel's war with Hamas and more than $9 billion for humanitarian assistance in Gaza "as well as other vulnerable populations around the world".