More than 300,000 people have fled Rafah in the week since Israel issued a partial evacuation order, the United Nations agency operating in Gaza said on Sunday.

The U.N. Agency for Palestine Refugees called the evacuation "forced and inhumane."

"There is nowhere safe to go," the agency said on social media, repeating the phrase three times for emphasis.

The Israeli military late Saturday called again for civilians to evacuate from much of the eastern part of the city, which is in southern Gaza.

Israel Defense Forces entered Rafah last week, in what they called a "precise" operation ahead of potential invasion.

"Prior to our operations we urge civilians to temporarily move towards humanitarian areas and move away from the crossfire that Hamas puts them in," the Israel Defense Forces said on a post on Telegram. "Our war is against Hamas, not against the people of Gaza."

-ABC News' Dragana Jovanovic and Kevin Shalvey

Israeli cabinet minister Benny Gantz has given Israeli Prime Minister Benjamin Netanyahu an ultimatum: approve a post-war plan by June 8, or he will resign, Gantz said at a press conference.

"While the Israeli soldiers show supreme bravery on the front, some of the men who sent them into battle behave with cowardice and irresponsibility," Gantz said.

A leader of the National Unity Party and a minister in the war cabinet, Gantz's resignation would not necessarily trigger the collapse of the government on its own, but would be politically significant.

The ultimatum come on the heels of a speech by defense minister Yoav Gallant, who is demanding a plan for the "day after" the war.

-ABC News' Jordana Miller and Dana Savir