By Nidal al-Mughrabi

CAIRO (Reuters) -Israeli firing and airstrikes killed at least 45 Palestinians across the Gaza Strip, many of them near an aid distribution site operated by the U.S.-backed Gaza Humanitarian Foundation on Saturday, local health authorities said.

Medics at Al-Awda and Al-Aqsa Hospitals in central Gaza areas, where most of the casualties were moved to, said at least 15 people were killed as they tried to approach the GHF aid distribution site near the Netzarim corridor.

The Israeli army said in a statement that an aircraft had opened fire on a person "to neutralise the threat" after he advanced towards troops and ignored warning shots fired near a group.

Last week, the army warned Palestinians not to approach routes leading to sites of the GHF between 6 p.m. and 6 a.m. local time, describing these roads as closed military zones. The GHF said none of its distribution centres was opened on Saturday.

The GHF began distributing food packages in Gaza at the end of May after Israel partially lifted a near three-month total blockade. Scores of Palestinians have been killed in near daily mass shootings trying to reach the food.

The United Nations rejects the Israeli-backed new distribution system as inadequate, dangerous and a violation of humanitarian impartiality principles.

"None of our distribution sites were open today, and there were no incidents at our sites because they were closed," the GHF said in a written response to Reuters about Saturday's incident.

The Gaza health ministry said in a statement on Saturday that at least 274 people have so far been killed, and more than 2,000 wounded, near aid distribution sites since the GHF began operations in Gaza.

Hamas, which denies Israeli charges that it steals aid, accused Israel of "employing hunger as a weapon of war and turning aid distribution sites into traps of mass deaths of innocent civilians."

Health officials at Shifa Hospital in Gaza said Israeli fire killed at least 12 Palestinians, who gathered to wait for aid trucks along the coastal road north of the strip.

The Israeli military ordered residents of Khan Younis and the nearby towns of Abassan and Bani Suhaila in the southern Gaza Strip to leave their homes and head west towards a so-called humanitarian zone, saying it would forcefully work against "terror organisations" in the area.

The war in Gaza erupted 20 months ago after Hamas-led militants raided Israel and took 251 hostages and killed 1,200 people, most of them civilians, on October 7, 2023, Israel's single deadliest day.

Israel's military campaign since has killed nearly 55,000 Palestinians, most of them civilians, according to health authorities in Gaza, and flattened much of the densely populated strip, which is home to more than two million people. Most of the population is displaced, and malnutrition is widespread.

Despite efforts by the United States, Egypt, and Qatar to restore a ceasefire in Gaza, neither Israel nor Hamas has shown willingness to back down on core demands, with each side blaming the other for the failure to reach a deal.

(Reporting and writing by Nidal al-Mughrabi; Editing by Toby Chopra, Louise Heavens, Peter Graff)