The Israeli military says it has launched the first stages of a new major offensive in Gaza, in a development that comes on the same day that US President Donald Trump concluded his visit to the region without securing a ceasefire deal.

The withering Israeli aerial campaign appeared to presage the ground operation Prime Minister Benjamin Netanyahu has vowed to launch if no ceasefire and hostage deal were struck by the time Trump returned to the U.

Israel has launched dozens of airstrikes across Gaza in attacks that local health officials say killed 108 people, mostly women and children, and which Israeli officials described as a prelude to a larger campaign to pressure Hamas to release hostages.