Gaza's Hamas-run health ministry has said at least 87 people were killed and more than 40 injured in Saturday's Israeli air strike on the city of Beit Lahia in the north of the Palestinian enclave.

The ministry said a number of people were still under the rubble after a residential area was hit.

Israel said it was checking reports of casualties but added that earlier - lower - figures published by Hamas were "exaggerated". In recent weeks, the Israel military has been carrying out intense bombardment of northern Gaza, saying it wanted to prevent Hamas fighters from regrouping there.

A senior UN official warned that the "nightmare in Gaza is intensifying" and the war "must stop now".

The UN's peace process co-ordinator, Tor Wennesland, said that "nowhere is safe in Gaza".

In a statement, Tor Wennesland said he condemned the continuing attacks on civilians.

"This war must end, the hostages held by Hamas must be freed, the displacement of Palestinians must cease, and civilians must be protected wherever they are. Humanitarian aid must be delivered unimpeded," he said.

In a statement on Sunday, Gaza's Hamas-run health ministry revised its death toll from 73 to 87 after the Israeli strike on Beit Lahia.

The earlier casualty figures were provided by Hamas late on Saturday.

The ministry also said that ambulance crews were unable to reach the site of the Israeli strike.

The Israel Defense Forces (IDF) described the strike as a "precision" attack on a "Hamas terror target". It told the BBC it was "doing everything possible to avoid causing harm to civilians".

Dr Eid Sabbah, Kamal Adwan Hospital's director of nursing, said the Israeli strike in Beit Lahia had completely destroyed several buildings, with "more than four, five residential blocks… razed to the ground".

The strikes targeted an entire residential square, Dr Sabbah said, in between Abu Jidian roundabout and Al Qassam mosque.

Dr Sabbah added that dozens of people were killed and many were wounded “some of whom reached the hospital, some of whom remain under the rubble”.

He urged for an end to the "siege" on hospitals in northern Gaza and "for life to return to normal… before it’s too late, before our nation is exterminated”.

Several images - including the one below - have since emerged on social media showing the treatment of the injured from Beit Lahia at the Kamal Adwan Hospital.

The images have been verified by the BBC as being from the hospital.

Israel confirmed the death of a senior army officer in northern Gaza's Jabalia area on Sunday.

Col Ahsan Daksa died after leaving his tank and being struck by an explosive, said IDF spokesman Rear Adm Daniel Hagari.

Three other officers were injured, one seriously, during the same incident.

Israel began a renewed military offensive in northern Gaza in early October, saying it was trying to prevent Hamas from regrouping in the area.

In particular, Israeli forces have surrounded and bombarded the densely-populated Jabalia area, which includes an urban refugee camp - with at least 33 people reported killed in a strike late on Friday.

Humanitarian groups have warned that virtually no aid has entered the area in the past few weeks. Israel's own statistics show that aid deliveries to Gaza as a whole have collapsed when compared with the same period in September.

On Saturday, the UN's top humanitarian official, Joyce Msuya, said that Palestinians in northern Gaza are enduring "unspeakable horrors" and called for these "atrocities" to stop.

Israel has repeatedly denied it is preventing humanitarian aid from entering Gaza - but on Tuesday the US told it to boost access within 30 days or risk having some American military assistance cut off.

At least 42,603 ​people have been killed and 99,795 injured in Gaza since the war began last October, the Hamas-run authorities say.

The war began after Hamas attacked Israel on 7 October 2023, leaving around 1,200 people dead and 251 taken to Gaza as hostages. Israel vowed to destroy Hamas in response, launching a ground offensive in the enclave.

Elsewhere, Israel continued its air strikes against the Lebanese group Hezbollah in the southern suburbs of Beirut on Sunday.

In a statement, the IDF said: "Earlier this morning, the IAF [Israel's air force] conducted an intelligence-based strike on a command centre of Hezbollah's intelligence headquarters and an underground weapons workshop in Beirut".

It added that several steps were taken to "reduce the possibility of civilian casualties", including "issuing advance warnings to residents".

The IDF also reported that about 160 rockets were fired from Lebanon into northern Israel.

Meanwhile, the Lebanese army said three of it soldiers were killed after a military vehicle was hit by an Israeli air strike in Nabatieh, southern Lebanon.

Israel has not yet commented.

Lebanon's army has historically stayed out of cross-border clashes between Israel and Hezbollah - but a number of its troops have been killed in Israeli attacks since fighting escalated last month.

Hezbollah - a powerful militant group in Lebanon - says it has been firing on Israeli positions in solidarity with Hamas in Gaza.

Both Hezbollah and Hamas are backed by Iran.