Thousands of Palestinians fled Saturday to southern Gaza seeking refuge after Israel warned them to evacuate before an expected ground offensive against Hamas.
Prime Minister Benjamin Netanyahu warned that nearly a week of fierce bombardment was just the beginning.
Israeli ground forces made "localized" raids into Gaza in the past 24 hours "to cleanse the area of terrorists and weaponry" and try to find "missing persons", the army said.
At least 1,900 Gazans -- most of them civilians and including more than 600 children -- have been killed in missile strikes on the densely populated enclave, the health ministry said.
"Where to go?" asked Umm Hossam, 29, who was among the thousands fleeing. "How long will the strikes and death last? We have no homes left, every area of Gaza is under threat," said the 29-year-old, her face streaked with tears, Hamas took about 150 Israeli, foreign and added said Friday that 13 of them had been killed in Israeli air strikes.
Hospitals are struggling to cope with the dead and wounded and the health system is "at a breaking point", the World Health Organization said.
In Jordan, after a meeting with Blinken, King Abdullah II called for "humanitarian corridors" to be opened urgently.
Egypt -- which runs the Rafah crossing to the south of Gaza -- faces the dilemma of accepting refugees with the possibility that Israel may never let them return.
But in Geneva, the Red Cross said the attacks on Israel could equally not justify "the limitless destruction of Gaza".
Hamas has said Palestinians rejected the evacuation request, yet thousands of Gazans were on the move in search of safety, carrying plastic bags of belongings, suitcases on their shoulders, and children in their arms.
Even before the evacuation order, more than 423,000 people had already fled their homes in Gaza, according to the UN. Arab League chief Ahmed Abul Gheit said Israel's evacuation order is a "forced transfer" that constitutes "a crime".
Palestinian president Mahmud Abbas said it would be "tantamount to a second Nakba" or "catastrophe", referring to the 760,000 Palestinians who fled or were expelled from their homes during the 1948 war that accompanied Israel's creation.
The Israeli military said on Saturday it had seen a "significant movement" south of Palestinian civilians, a day after ordering Gaza City residents to flee.
Israel has put the Hamas-run Gaza Strip, home to 2.3 million Palestinians, under a total siege and bombarded it with unprecedented air strikes. Gaza authorities say 1,900 people have died.
On Friday, more than one million residents of northern Gaza received a notice from Israel to flee south within 24 hours, a deadline that passed at 5 a.m. (0200 GMT).
"We have seen a significant movement of Palestinian civilians towards the south," Israeli military spokesperson Lieutenant Colonel Jonathan Conricus told a video briefing early on Saturday.