The UN humanitarian chief has urged Israel to open more channels to increase aid to Gaza.

The chief's comments come after Israel warned it could cut off supplies to Gaza if Hamas does not release the bodies of dead hostages soon.

UN humanitarian chief Tom Fletcher has called on both sides to implement a recently agreed ceasefire to avoid undermining a crucial US-brokered deal.

The delay in returning the bodies of the hostages has angered Israel, and the Rafah crossing into Gaza, between Egypt and southern Gaza, was closed on Wednesday.

Gaza residents are stockpiling supplies, fearing that the agreement may not last, and food prices have skyrocketed.

The UN official also expressed deep concern over the attacks on civilians in Gaza.

Reports indicate that unidentified Hamas militants have publicly executed eight Palestinians, sparking fears among Gaza residents.

Israel has returned 45 Palestinian hostages, the Hamas-run Health Ministry confirmed on Wednesday.

This brings the total number of bodies returned by Israel to 90.