Thousands of desperate Palestinians have stormed a United Nations warehouse in central Gaza, with the World Food Programme reporting two possible deaths in the tumult.

The humanitarian situation in Gaza, where aid has finally begun to trickle in after a two-month blockade, is dire following 18 months of devastating war. Food security experts say starvation is looming for one in five people.

Footage showed crowds of Palestinians breaking into a WFP warehouse in Deir Al-Balah on Wednesday and taking bags of emergency food supplies as gunshots rang out.

"Hordes of hungry people broke into WFP's Al-Ghafari warehouse in Deir Al-Balah, central Gaza, in search of food supplies that were pre-positioned for distribution," WFP said.

"Initial reports indicate two people died and several were injured in the tragic incident," WFP said, adding that it was still confirming details.

Israel accused the United Nations Wednesday of seeking to block Gaza aid distribution, as the global body said it was doing its utmost to facilitate distribution of the limited assistance greenlit by Israel's authorities.

The issue of aid has come sharply into focus amid starvation fears and intense criticism of the Gaza Humanitarian Foundation (GHF), a private US-backed aid group that has bypassed the longstanding UN-led system in the territory.

Stephane Dujarric, spokesman for UN secretary-general Antonio Guterres, reiterated the world body's opposition to coordinating with GHF.

"We will not participate in operations that do not meet our humanitarian principles," Dujarric said.

He said the UN was doing all it could to send aid, adding that since last week 800 truckloads were approved by Israel but fewer than 500 made it into Gaza. (AFP)