The Israeli attack on a school in the Gaza Strip to eliminate Hamas fighters has sparked fierce criticism and heated international debate.
A spokesman for the UN Human Rights Office told dpa in Geneva on Friday that international humanitarian law "prohibits launching attacks where the anticipated incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, would be excessive in relation to the concrete and direct military advantage expected to be obtained from this specific attack."
Parties to the conflict must take all precautions to avoid or minimise the loss of civilian life, injury to civilians and damage to civilian objects, the UN spokesman said.
This includes "issuing advance warnings when feasible; and suspending an attack if it becomes apparent that it does not any longer respect the principles of necessity, distinction and proportionality," he said.
Dozens of civilians were killed in an Israeli airstrike on a school run by the UN agency for Palestinian refugees (UNRWA) in central Gaza, Palestinian medics and the Hamas militant group said on Thursday, a claim Israel denied.
The Hamas-controlled health authority in Gaza said that at least 30 people were killed in the attack on Wednesday night and that most of the victims were women and children. Hamas said 40 people died.
What exactly is proportionate is not defined in the provisions of international law, and what would no longer be proportionate can only be determined by courts that take all aspects into account. The same applies to war crimes or crimes against humanity, where only courts can make definitive statements.