Aid trucks rolled into Gaza on Wednesday and Israel resumed preparations to open the main Rafah crossing after a dispute over the return of the bodies of dead hostages that had threatened to derail the fragile ceasefire deal with Hamas.

Israel had threatened to keep Rafah shut and reduce aid supplies because Hamas was returning bodies too slowly, showing the risks to a truce that has stopped two years of devastating warfare in Gaza and freed all living hostages held by Hamas.

However, the militant group returned more Israeli bodies overnight, and an Israeli security official said on Wednesday preparations were under way to open Rafah to Gazan citizens, while a second official said 600 aid trucks would go in.

Hamas returned four bodies confirmed as dead hostages on Monday and another four bodies late on Tuesday, though Israeli authorities said one of those bodies was not that of a hostage.

The dispute over the return of bodies still has the potential to upset the ceasefire deal along with other major issues that are yet to be resolved.

Later phases of the truce call for Hamas to disarm and cede power, which it has so far refused to do. It has launched a security crackdown, parading its power in Gaza through public executions and clashes with local clans.

Longer-term elements of the ceasefire plan including how Gaza will be governed, the make-up of an international force to take over there and moves towards the creation of a Palestinian state have yet to emerge.

Twenty-one bodies of hostages remain in Gaza, though some may be very hard to find or recover because of destruction during the conflict. An international task force is meant to find them.

The deal also requires Israel to return the bodies of 360 Palestinian militants killed in battle. The first group of 45 was handed over on Tuesday and were being identified, said Palestinian health authorities.

The war has caused a humanitarian catastrophe in Gaza, with nearly all inhabitants driven from their homes, a global hunger monitor saying famine was present in the enclave and health authorities overwhelmed.

A first group of trucks moved from the Egyptian side of the border into the Rafah crossing at dawn on Wednesday, some tankers carrying fuel and others loaded with pallets of aid.

However, it was not clear if that convoy would complete its crossing into Gaza as part of the 600 trucks that were due to enter the enclave on Wednesday – the full daily complement required under the ceasefire plan. Aid trucks entered Gaza through other crossings.

"Humanitarian aid continues to enter the Gaza Strip through the Kerem Shalom Crossing and other crossings after Israeli security inspection," the Israeli security official said.

Israel's public broadcaster Kan reported that Wednesday's aid deliveries would include food, medical supplies, fuel, cooking gas and equipment to repair vital infrastructure. (Reuters)