DEIR AL-BALAH, Gaza Strip — An Israeli strike hit a street in central Gaza on Thursday where witnesses said a crowd of people was getting bags of flour from a Palestinian police unit that had confiscated the goods from gangs looting aid convoys. Hospital officials said 18 people were killed.

The strike was the latest violence surrounding the distribution of food to Gaza’s population, which has been thrown into turmoil over the past month. After blocking all food for 2 1/2 months, Israel has allowed only a trickle of supplies into the territory since mid-May.

Efforts by the United Nations to distribute the food have been plagued by armed gangs looting trucks and by crowds of desperate people offloading supplies from convoys.

The strike in the central town of Deir al-Balah on Thursday appeared to target members of Sahm, a security unit tasked with stopping looters and cracking down on merchants who sell stolen aid at high prices. The unit is part of Gaza’s Hamas-led Interior Ministry, but includes members of other factions.

Witnesses said the Sahm unit was distributing bags of flour and other goods taken from looters and corrupt merchants, drawing a crowd when the strike hit.

There was no immediate comment from the Israeli military. Israel has accused the militant Hamas group of stealing aid and using it to prop up its rule in the enclave. Israeli forces have repeatedly struck Gaza’s police, considering them a branch of Hamas.

An association of Gaza’s influential clans and tribes said Wednesday they have started an independent effort to guard aid convoys to prevent looting. The National Gathering of Palestinian Clans and Tribes said it helped escort a rare shipment of flour that entered northern Gaza that evening.

It was unclear, however, if the association had coordinated with the U.N. or Israeli authorities. The World Food Program did not immediately respond to requests for comment by The Associated Press.

“We will no longer allow thieves to steal from the convoys for the merchants and force us to buy them for high prices,” Abu Ahmad al-Gharbawi, a figure involved in the tribal effort, told the AP.

Israeli Prime Minister Benjamin Netanyahu and Defense Minister Israel Katz in a joint statement Wednesday accused Hamas of stealing aid that is entering northern Gaza, and called on the Israeli military to plan to prevent it.

The National Gathering slammed the statement, saying the accusation of theft was aimed at justifying the Israeli military’s “aggressive practices.” It said aid was “fully secured” by the tribes, which it said were committed to delivering the supplies to the population.

The move by tribes to protect aid convoys brings yet another player in an aid situation that has become fragmented, confused and violent, even as Gaza’s more than 2 million Palestinians struggle to get food.

Throughout the more than 20-month-old war, the U.N. led the massive aid operation by humanitarian groups providing food, shelter, medicine and other goods to Palestinians even amid the fighting. U.N. and other aid groups say that when large amounts of supplies are allowed in, looting and theft dwindles.

Israel, however, seeks to replace the U.N.-led system, saying Hamas has been siphoning off large amounts of supplies from it, a claim the U.N. and other aid groups deny.

Israel has backed an American private contractor, the Gaza Humanitarian Foundation, which has started distributing food boxes at four locations, mainly in the far south of Gaza for the past month.

Thousands of Palestinians walk for hours to reach the hubs, moving through Israeli military zones where witnesses say Israeli troops regularly open fire with heavy barrages to control the crowds.

Separately, Israeli strikes overnight and early Thursday killed at least 28 people across the Gaza Strip, according to the territory’s Health Ministry.