The UN secretary-general has called for an independent investigation into the killing of Palestinians near an aid distribution centre in Gaza on Sunday, amid disputed reports that Israeli forces had opened fire.

Witnesses reported being shot at while waiting for food from the centre in Rafah run by the US and Israel-backed Gaza Humanitarian Foundation (GHF).

The Red Cross said its hospital received 179 casualties, 21 of whom were dead. The Hamas-run Civil Defence agency put the death toll at 31.

On Sunday, the Israeli military denied its troops fired at civilians near or within the site and said reports to this effect were false.

The GHF said the reports were “outright fabrications” and that it was yet to see evidence of an attack at or near its facility.

Israel does not allow international news organisations, including the BBC, into Gaza, making verifying what is happening in the territory difficult.

UN Secretary-General Guterres said in a statement on Monday: “I am appalled by the reports of Palestinians killed and injured while seeking aid in Gaza yesterday.

“I call for an immediate and independent investigation into these events and for perpetrators to be held accountable.”

Israel’s foreign ministry responded by branding his comments a “disgrace” in a post on X, and criticised him for not mentioning Hamas.

The Civil Defence agency said 31 people were killed and 176 wounded “after Israeli gunfire targeted thousands of civilians near the American aid centre in Rafah” early on Sunday morning.

According to the International Committee of the Red Cross (ICRC), the Red Cross Field Hospital in Rafah received a “mass casualty influx” of 179 cases, including women and children, at that time.

The majority suffered gunshot or shrapnel wounds, and 21 were declared dead upon arrival, it said, adding “all patients said they had been trying to reach an aid distribution site”.

Médecins Sans Frontières (MSF) said its teams at Nasser hospital in Khan Younis also treated people with serious injuries, some of whom were in a critical condition.

It added the patients “reported being shot at from all sides by Israeli drones, helicopters, boats, tanks and soldiers”, and that one staff member’s brother was “killed while attempting to collect aid from the distribution centre”.

A journalist in Rafah told the BBC a crowd of Palestinians had gathered near al-Alam roundabout in Rafah, close to the GHF’s site, when Israeli tanks approached and opened fire.

One video posted online on Sunday morning appeared to show Palestinians taking cover in an open area of sandy terrain while what sounds like automatic gunfire rings out. However, the BBC was unable to verify the location because there are not enough features visible.

The Israel Defense Forces (IDF) put out a statement on Sunday afternoon that said an initial inquiry indicated its troops “did not fire at civilians while they were near or within the humanitarian aid distribution site and that reports to this effect are false”.

Spokesman Brig Gen Effie Defrin accused Hamas of “spreading rumours” and “trying bluntly and violently to stop the people of Gaza from reaching those distribution centres”.

The IDF also released drone video it said showed armed men firing at civilians on their way to collect aid, although the BBC was unable to verify where or when it was filmed.

Later on Sunday, an Israeli military official briefed reporters that soldiers had acted to “prevent a number of suspects from approaching the forces” approximately 1km from the GHF site, before it opened.

“Warning shots were fired,” the official said, before insisting there was “no connection between the incident in question and the false allegations against the IDF”.

The GHF said in a statement on Monday that the reports were “the most egregious in terms of outright fabrications and misinformation fed to the international media community.

“There were no injuries, fatalities or incidents during our operations yesterday. Period. We have yet to see any evidence that there was an attack at or near our facility.”

The US ambassador to Israel, Mike Huckabee, accused major news outlets of “reckless and irresponsible reporting” on the matter.

“Drone video and first-hand accounts clearly showed that there were no injuries, no fatalities, no shooting, no chaos,” he said on Monday.

“The only source for these misleading, exaggerated, and utterly fabricated stories came from Hamas sources, which are designed to fan the flames of antisemitic hate that is arguably contributing to violence against Jews in the United States,” he added.

Meanwhile on Monday, health officials and local media reported that another three Palestinians were killed by Israeli fire near the same GHF centre in Rafah’s Tal al-Sultan area.

A Red Cross spokesman told the Associated Press that its field hospital in Rafah received 50 wounded people, mostly with gunshot and shrapnel wounds, including two declared dead on arrival, while Nasser hospital in nearby Khan Younis said it received a third body.

The Israeli military said in a statement that “warning shots were fired toward several suspects who advanced toward” troops approximately 1km from the site.

The military added it was “aware of reports regarding casualties, and the details of the incident are being thoroughly looked into”.

Also on Monday, the Civil Defence reported that 14 people, including six children and three women, were killed in an Israeli strike on a house in the northern town of Jabalia. More than 20 others were believed to be missing under the rubble of the destroyed building, it said.

There was no immediate comment from the IDF, but it said in a statement that its aircraft had struck dozens of targets across Gaza over the past day, including “military structures belonging to terror organisations”, underground tunnels, and weapons stores.

Israel imposed a total blockade on Gaza on 2 March and resumed its military offensive two weeks later, collapsing a two-month ceasefire with Hamas. It said the steps were meant to put pressure on the armed group to release the 58 hostages still held in Gaza, at least 20 of whom are believed to be alive.

On 19 May, the Israeli military launched an expanded offensive that Prime Minister Benjamin Netanyahu said would see troops “take control of all areas” of Gaza. The following day, he said Israel would also temporarily ease the blockade and allow a “basic” amount of food into Gaza.

Israel launched a military campaign in Gaza in response to Hamas’ cross-border attack on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

At least 54,470 people have been killed in Gaza since then, including 4,201 since Israel resumed its offensive, according to the territory’s Hamas-run health ministry.