More than 700 Palestinians were killed overnight by Israeli air strikes, Gaza’s Hamas-run health ministry said on Tuesday, the highest 24-hour death toll in Israel’s two-week-old “total siege”, as pressure grew for aid to be allowed into the enclave unimpeded.

The Israeli military said it had hit over 400 Hamas militant targets and killed dozens of its fighters overnight, but that it would take time to destroy Gaza’s ruling Islamist group, whose deadly cross-border attack on October 7 shocked Israel.

With international aid agencies warning of a humanitarian catastrophe unfolding in Gaza, French President Emmanuel Macron flew to Israel to offer it support.

Macron told Prime Minister Benjamin Netanyahu that France stood “shoulder to shoulder” with Israel in its war with Hamas but that it must not fight “without rules”. Netanyahu said Israel would try to protect civilians as it worked to ensure they “will no longer live under Hamas tyranny”.

United Nations agencies called “on our knees” on Tuesday for emergency aid to be allowed unimpeded into Gaza, saying more than 20 times current deliveries were needed to support its Palestinian population after two weeks of Israeli bombardment.

The World Health Organization, in the latest of increasingly desperate UN appeals, called for “an immediate humanitarian ceasefire” to allow safe deliveries of aid.

Doctors in Gaza say patients arriving at hospitals are showing signs of disease caused by overcrowding and poor sanitation after more than 1.4 million people fled their homes for temporary shelters under Israel’s heaviest-ever bombardment.

But there appeared to be little prospect of a ceasefire any time soon in the bloodiest episode in the Israeli-Palestinian conflict for decades.

Gaza’s health ministry said at least 5,791 Palestinians have been killed by Israeli bombardments of the densely populated territory since October 7, including 2,360 children. A total of 704 were killed in the previous 24 hours alone, it said.

Ministry spokesman Ashraf Al-Qidra said it was the highest 24-hour number of deaths in the two weeks of Israeli bombing.

After an air strike in Khan Younis, Abdallah Tabash held his dead daughter Sidra, refusing to let go as he held her bloodstained face and hair. “I want to look at her as much as I can,” he said.

Israeli tanks and troops are massed on the border between Israel and the enclave awaiting orders for an expected ground invasion – an operation that may be complicated by fears for the hostages’ welfare and militants heavily armed by Iran dug into a crowded urban setting using a vast network of tunnels.

The bombardments were unleashed in response to a shock cross-border Hamas assault into southern Israel in which gunmen killed over 1,400 people – mostly civilians – in a single day.Hamas on Monday freed two Israeli women who were among the more than 200 hostages taken during the rampage – the third and fourth to be released.

Yocheved Lifshitz, 85, said she was beaten by militants as she was abducted and had difficulty breathing. “They stormed into our homes. They beat people. They kidnapped others, the old and the young without distinction,” she said, seated in a wheelchair and speaking in barely a whisper to reporters.

“I’ve been through hell,” Lifshitz said.

Inside Gaza, a group of hostages were led into what Lifshitz called a “spider’s web” of damp tunnels and eventually reached a large hall where, under 24-hour guard, a doctor visited every other day and brought them medicines they needed.

“They treated us gently and met all our needs,” she said.

Among the targets Israel said it hit overnight was a tunnel that allowed Hamas to infiltrate Israel from the sea, as well as Hamas command centres in mosques, it said. Reuters could not verify the report.

Wide areas of highly urbanised Gaza have been demolished by Israeli bombs, forcing more than half of its 2.3 million people to seek shelter elsewhere in the territory. Food, clean water, medicine and fuel are fast running out.

Residents said several people were killed or wounded when an Israeli missile hit a petrol station in Khan Younis, where people who fled the eastern side of the city were gathered to charge their devices and fill water canisters.

“They bombed them in their sleep,” said Abdallah Abu Al-Atta, who lives by the petrol station.

More than 40 medical centres halted operations after they ran out of fuel or were damaged by Israeli bombing, the health ministry spokesman said.

How soon Israel might launch a full-scale invasion of Gaza remains unclear. The Middle East’s most powerful military faces a group that has built up a powerful arsenal with Iran’s help.

World powers are concerned the conflict could ignite the entire region and some have urged Israel to exercise restraint, while affirming its right to self-defence.

The outcome is unclear: Palestinian hopes for an independent state in Israeli-occupied territory were already remote, with peace talks a distant memory and Netanyahu’s right-wing government expanding Jewish settlements in the West Bank.

Deadly clashes have worsened between the Israeli military and Palestinians in the West Bank, and resurged between Israel and Lebanon’s Iran-backed Hezbollah group along the two countries’ volatile border.

Fears of regional escalation focus on Iran’s network of proxies in Syria, Iraq and Yemen. Any wider conflagration would jeopardise security in a region key to global energy supplies. US officials told Reuters the US military is taking new steps to protect its troops in the Middle East as concerns mount about attacks by Iran-backed groups, and it is leaving open the possibility of evacuations of military families if needed.

• A Reuters report