JERUSALEM — A new Israeli-backed aid group opened a third hub in the Gaza Strip on Thursday to try to get more food to a desperate population. But more chaotic scenes unfolded during the opening, similar to the launch of the first center this week.

The United Nations and other aid organizations have declined to cooperate with the new aid group, the Gaza Humanitarian Foundation, describing it as a militarized distribution operation that violates humanitarian principles.

On Thursday, crowds of hungry Palestinians scrambled for handouts and dodged stun grenades that were fired outside the new aid hub to disperse crowds, according to videos verified by The New York Times. Some, carrying their aid bundles, climbed over earthen walls surrounding the site in Al-Bureij, in central Gaza. It was unclear who had fired the stun grenades, but the Israeli military denied involvement. A day earlier, a large crowd of desperate Palestinians broke into a warehouse run by the U.N.’s World Food Program in Gaza in search of food and flour. Program officials said initial reports indicated that two people had been killed.

On Tuesday, at the chaotic launch of the new aid initiative, thousands of hungry Palestinians rushed another food distribution site, prompting Israeli forces outside the compound to fire warning shots to disperse the crowds.

The Gaza Humanitarian Foundation said Thursday that “nonlethal means” had been used to disperse crowds that were refusing to leave the new aid hub, but that no one was injured. The foundation did not say who had opened fire. The Israeli military denied firing near the hub Thursday. The foundation is run by private American companies, with Israeli forces guarding the compounds’ perimeter.

The new aid operation is intended to bypass Hamas, which Israel accuses of siphoning off aid, selling it for profit and using it as a tool to control Palestinians.

The U.N. says the new system is woefully insufficient to meet the basic needs for Palestinians’ survival after an 80-day Israeli blockade brought much of the territory to the brink of famine. Hundreds of distribution points existed under the previous U.N. aid-distribution system. But the new system had only three locations operating by Thursday, up from two Wednesday.

Separately from the new system, some U.N. aid trucks are 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.

The United Nations said Israeli authorities had cleared about 800 truckloads of aid since the blockade was lifted last week. Only about 200 of them have moved out to the population, however, because of the dangers surrounding aid distribution.

The Gaza Humanitarian Foundation said Thursday that it had distributed enough supplies throughout the day for nearly 1 million meals and that, in total to date, it had distributed about 17,200 boxes of provisions, enough for more than 1.8 million meals.