Palestinians say Israeli forces opened fire on people trying to access a U.S.-backed group's aid distribution hub in Gaza, in the deadliest of such incidents reported to date.

The UN human rights chief said Israel's "means and methods of warfare" were inflicting "horrifying, unconscionable suffering".

The U.S.-backed Gaza Humanitarian Foundation (GHF) stated late on Wednesday that Hamas “brutally attacked” a bus of Palestinians working for the aid organization while en route to one of their distribution sites.