At least 20 Palestinians were killed on Wednesday at an aid distribution site run by the Gaza Humanitarian Foundation, in what the U.S.-backed group said was a crowd surge instigated by armed agitators.
The GHF, which is supported by Israel, said 19 people were trampled and one fatally stabbed during the crush at one of its centres in Khan Younis in southern Gaza.
"We have credible reason to believe that elements within the crowd – armed and affiliated with Hamas – deliberately fomented the unrest," GHF said in a statement.
Hamas health officials told Reuters that 21 people had died of suffocation at the site.
Unreliable figures as they come from the Islamist organization.
The GHF uses private U.S. security and logistics companies to get supplies into Gaza, largely bypassing a U.N.-led system that Israel alleges has let Hamas-led militants loot aid shipments intended for civilians. Hamas denies the accusation.
The U.N. has called the GHF’s model unsafe and a breach of humanitarian impartiality standards - an allegation GHF has denied.
Earlier on Wednesday, the Israeli military said it had finished paving a new road in southern Gaza separating several towns east of Khan Younis from the rest of the territory in an effort to disrupt Hamas operations.
Palestinians see the road, which extends Israeli control, as a way to put pressure on Hamas in ongoing ceasefire talks, which started on July 6 and are being brokered by Arab mediators Egypt and Qatar with the backing of the United States.
Palestinian sources close to the negotiations said a breakthrough had not yet been reached on any of the main issues.
Hamas said it rejected an Israeli demand to keep at least 40% of Gaza under its control as part of any deal. Hamas also demanded the dismantlement of the GHF and the reinstatement of a U.N.-led aid delivery mechanism.
Senior Hamas official Basem Naim said in a post on his Facebook page that the road showed Israel was not serious about reaching a ceasefire deal and confirms "the occupation’s long-term intentions and plans to remain inside the Strip".
Israeli Prime Minister Benjamin Netanyahu says the war will end once Hamas is disarmed and removed from Gaza.
By Nidal al-Mughrabi and Crispian Balmer