Canadian Prime Minister Justin Trudeau on Tuesday said the "killing of women, of children, of babies" in the besieged Gaza Strip must end, in his sharpest criticism of Israel since war against Hamas broke out over a month ago.

Canada has maintained that Israel has the right to defend itself against Hamas after the Palestinian militant group attacked southern Israel last month, killing 1,400 people and taking over 200 hostage. But like the United States and other allies, it has expressed increasing concern over the mounting death toll in the battered enclave, where local health officials say 11,000 people have been killed since the conflict started.

"I urge the government of Israel to exercise maximum restraint. The world is watching, on TV, on social media - we're hearing the testimonies of doctors, family members, survivors, kids who have lost their parents," he said.

"The world is witnessing this killing of women, of children, of babies. This has to stop," he told a news conference in the western province of British Columbia.

The lives of 36 babies at Gaza's Al Shifa Hospital were hanging in the balance on Tuesday, according to medical staff there who said there was no clear mechanism to move them despite an Israeli effort to supply incubators for an evacuation.

Three of the original 39 premature babies have already died since Gaza's biggest hospital ran out of fuel at the weekend to power generators that had kept their incubators going.

Trudeau also said Hamas needed to stop using Palestinians as human shields and should release all its hostages.

Around 350 Canadian citizens, permanent residents and family members had been evacuated from Gaza, he added.

Last week Trudeau called for a significant humanitarian pause in the conflict to allow for the release of all hostages and the delivery of enough aid to address civilian needs.