As Israel warns more Gaza neighborhoods to evacuate, a top U.N. envoy told the United Nations Security Council on Thursday that Israel would be required under international law to take responsibility for helping Palestinians civilians in any further large-scale displacements.

The United Nations is struggling to cope with a flood of some 220,000 Palestinian civilians into shelters. They have come under fire during three weeks of fighting between Israel and Hamas militants who dominate Gaza.

Speaking from Gaza City, Pierre Krähenbühl, head of the U.N. Relief and Works Agency (UNRWA), said the impoverished enclave of 1.8 million Palestinians was facing a precipice. Krähenbühl said he was alarmed to hear that Israel had warned more neighborhoods in Gaza to evacuate ahead of military action.