The UN secretary general, António Guterres has warned Israel could carry out the “ethnic cleansing” of Gaza if the international community does not make a determined stand to prevent it.

Guterres made his appeal at a time of mounting civilian casualties from the Israeli bombardment of northern Gaza. A strike on Tuesday in Beit Lahiya district killed at least 93 people, in what the UN said was just one of at least seven “mass casualty incidents” across Gaza in the past week.

At the same time, aid deliveries to Gaza are reported to have fallen to their lowest level since the start of the war, leading to growing allegations that Israel’s true intention is to drive the remaining Palestinian population out of at least part of Gaza.

The UN secretary general, speaking on the sidelines of the COP16 biodiversity conference in Colombia, suggested that the “ethnic cleansing” of Gaza had been prevented until now by its people’s refusal to succumb to the intense pressure to flee their homes and by Arab resolve not to accept mass population transfers.

“The intention might be for the Palestinians to leave Gaza, for others to occupy it,” Guterres told the Guardian. “But there has been – and I pay tribute to the courage and the resilience of the Palestinian people and to the determination of the Arab world – [an effort] to avoid the ethnic cleansing becoming a reality.

“We will do everything possible to help them remain there and to avoid ethnic cleansing that might occur if there is not strong determination from the international community,” he added.

Jordan’s foreign secretary, Ayman Safadi, last week told the US secretary of state, Antony Blinken that ethnic cleansing was already happening in Gaza. Israel’s military denies systematically trying to force Palestinians from the territory.

There has been broad international condemnation of Tuesday’s bombing of a five-storey residential building in Beit Lahiya, in which there were many children among the 93 fatalities. The US called it “a horrifying incident with a horrifying result” and on Wednesday the French foreign ministry said it condemned the bombing and “recent Israeli strikes on hospitals in the north”.

“The siege imposed on north Gaza must be ended immediately,” the French statement said.

The Israel Defense Forces (IDF) said it was aware of the reports of civilian casualties in Beit Lahiya and was looking into it.

Israel’s defence minister, Yoav Gallant, urged IDF troops to “continue exerting as much [military] pressure on Hamas as possible” to bring about the return of Israeli hostages. The Mossad director, David Barnea, met his CIA counterpart, Bill Burns, and the Qatari prime minister, Mohammed Al Thani, in Doha earlier in the week amid reports of a new proposal for a short-term truce to allow some civilian respite and the return of hostages held by Hamas, but there was no confirmation of a breakthrough after five months of talks.

Israel kept up its bombing campaign in Lebanon against Hezbollah, calling on the resident population to leave the Baalbek region in the north-east of the country. Lebanon’s health ministry later said at least 19 people, including eight women were killed in separate Israeli strikes in the region.

Hezbollah’s new leader, Naim Qassem, said on Wednesday he would agree to a ceasefire with Israel under terms Hezbollah found acceptable but said a viable deal had yet to be presented.

In Gaza, the intense bombardment of Beit Lahiya continued with 19 people killed in separate strikes overnight, and 10 more deaths on Wednesday. The injured people and the dead were taken on donkey carts to the nearby Kamal Adwan hospital, which is barely functional after medical staff have fled or reportedly been detained, and medical supplies and fuel are almost completely depleted.

“Only two … out of 20 health service points and two hospitals, Kamal Adwan and Al-Awda, remain functional, although partially, hampering the delivery of life-saving health services,” the UN humanitarian affairs agency, OCHA, said in a daily bulletin.

“Across the Gaza Strip, October has seen very limited food distribution due to severe supply shortages,” the agency said. It said 1.7 million people, 80% of the population, did not receive rations.

Philippe Lazzarini, the head of the UN relief agency for Palestinian refugees (Unrwa), said on X: “Today, even as we look into the faces of children in Gaza, some of whom we know will die tomorrow, the rules-based international order is crumbling in a repetition of the horrors that led to the establishment of the United Nations, and in violation of commitments to prevent their recurrence.”

On Monday, the Israeli Knesset voted to ban Unrwa operations in the country within the next three months, in defiance of near-unanimous global appeals, which could further prevent aid distribution in Gaza and the West Bank.