A stampede outside an aid distribution center in southern Gaza killed at least 20 people who were waiting for food on Wednesday, according to Palestinian and aid officials, the latest in a string of deadly episodes around sites run by the Israeli-backed Gaza Humanitarian Foundation.

The deaths bring the number of people killed while trying to get food from the organization to about 700 since late May, according to data provided this week by the United Nations.

There were conflicting reports about the melee, which started on Wednesday morning on the outskirts of Khan Younis, the largest city in southern Gaza.

The Gaza Health Ministry said tear gas was fired into a crowd gathered at the distribution site, causing a stampede. It said 21 people were killed, 15 of whom suffocated.

The aid organization said that 20 people were killed after armed agitators among a gathering crowd at its Khan Younis distribution site created a “chaotic and dangerous surge.” Nineteen of the victims were trampled and one was stabbed, the organization said in a statement, adding that it was “heartbroken.”

It was not immediately possible to explain the discrepancy in the death toll.

In the statement, the aid organization asserted there was “credible reason to believe that elements within the crowd — armed and affiliated with Hamas — deliberately fomented the unrest.” Those claims could not be independently verified.

In a follow-up message to The New York Times, the aid group called claims that it had shot tear gas into the crowd “completely false.” It said it had used a “limited” amount of pepper spray, but “only to safeguard additional loss of life.” At one point, it said, an American worker had to enter the crowd to rescue a child from being trampled.

The Israeli military declined to comment on the episode and referred questions to the aid organization.

The Gaza Humanitarian Foundation was created to distribute food in Gaza as Israel faced widespread international condemnation for a two-month aid blockade that brought the enclave to the brink of famine. Israeli officials had said the blockade was an attempt to force Hamas to surrender and release the remaining hostages held in Gaza.

Since the organization started operations in late May, thousands of desperate and hungry Palestinians have come to its four aid sites early each morning hoping to obtain food. Hundreds have since been killed by gunfire that eyewitnesses and Gaza health officials have blamed on Israeli forces shooting into the crowds.

On Wednesday, Gaza’s Health Ministry described the distribution sites as “death traps” in a statement that blamed Israel and the United States for “deliberately committing massacres in a systematic manner and using various methods against the starving people.”

Video footage posted by local journalists on social media and verified by The New York Times showed people rushing several men in the back of a vehicle, some appearing lifeless, to the emergency entrance at the Nasser Medical Complex, the main medical facility in Khan Younis.

“Let the world see!” one man shouted in the video as the vehicle sped toward the hospital.

In another video, also verified by The Times, a man, who could not be independently identified, said aid workers at the Khan Younis site had refused to open the gates for the people who had gathered at the distribution center and were overcrowded as they waited. Some people then climbed over the gate to get to the aid, according to the man, who was covered in dust and helping carry a man who he said had suffocated to death to the hospital.

The Gaza Humanitarian Foundation said this week it has distributed more than 76 million meals since May. But the group said false information circulating online about access to some of its sites have driven large crowds to closed centers, fueling confusion and disorder.

Many Gazans have had to walk for miles and cross Israeli military cordons to obtain aid from the group’s distribution sites, most of which have not been operational on most days. The sites are in southern and central Gaza, which critics said would help Israel’s attempts to displace residents from the northern part of the territory.

The United Nations has said the group’s supplies constitute a mere trickle of assistance compared with the needs of a population of about two million people at risk of famine.

Some U.N. aid trucks are still making their way through a single border crossing into southern Gaza. But U.N. officials say that distribution to warehouses and bakeries inside Gaza has been hampered by the lack of secure routes, and that negligible quantities of food are reaching the people who need it.

Gaza’s Health Ministry said that U.N. trucks carrying medical supplies were expected to enter the territory on Thursday, and called on the public to protect them from attacks and ensure their safe passage to hospitals.

Not far from the site of the stampede, the Israeli military said it had opened a new security corridor to divide the city of Khan Younis into eastern and western sectors to isolate Hamas units. Some areas of the city have been evacuated several times, displacing thousands of people and pushing them into crowded zones near the Egyptian border.

Abu Bakr Bashir contributed reporting.