The United Nations called Tuesday for international investigators to be granted access to all of Gaza "to assist with evidence-gathering" as hundreds of bodies are pulled from the rubble.

The ongoing recovery of extensive human remains in Gaza, mostly of women and children, nearly three years after Israel heavily bombed their homes, highlights the possibility that war crimes have been committed, the UN warned.

"The remains of what appears to be entire families are now being unearthed at locations that were pulverised by Israeli attacks," UN rights chief Volker Turk said in a statement.

"I worry the remains recovered so far may only be the tip of the iceberg," he said, pointing to how much of Gaza has been flattened by Israeli bombing or demolition and clearing by heavy machinery.

The UN rights office said it was critical that evidence of violations, including at destroyed sites, be gathered, calling for international investigators to be allowed into all parts of Gaza.