A senior UN source said UN humanitarian agencies were compiling evidence of war crimes and referring it to the "highest levels".
Some human rights activists allege Israeli leaders ordered military casualties be kept low no matter what cost to civilians, and that the strategy contributed to one of the bloodiest Israeli assaults on Palestinian territories.
John Ging, head of the UN Palestinian refugee agency in Gaza, said: "It's about accountability [over] the issue of the appropriateness and proportionality of the force used, and the duty of care of civilians. We don't want to join any chorus of passing judgement, but there should be an investigation of every incident where there are concerns there might have been violations in international law."
The Israeli military are accused of:
- Using powerful shells in civilian areas that the army knew would cause many innocent casualties;
- Using banned weapons such as phosphorus bombs;
- Holding Palestinian families as human shields;
- Attacking medical facilities, including killing 12 ambulance men in marked ambulances; and
- Killing large numbers of policeman with no military role.