The U.S. Embassy in Jerusalem on Sunday morning urged U.S. citizens trapped in the Gaza Strip to move to southern Gaza along the main highway, the Salah al-Din Street.

U.S. citizens who can do so safely were advised by the embassy to flee to the south of the Gaza Valley toward the city of Khan Younis as U.S. officials work on potential options for getting them out of Gaza.

8:01

Is Israel’s ground invasion of Gaza imminent?

ABC News Chief National Correspondent Matt Gutman joins ABC News’ Phil Lipof to break down the potential timeline for Israel’s pending ground offensive in Gaza.

As of Sunday morning, the only exit to the south of Gaza, the Rafah crossing at the Egyptian border, remained closed to all seeking to flee Gaza, officials said.

But Tala Herzallah, a Palestinian woman trapped in Gaza, told ABC News Sunday that Israel Defense Forces are continuing to bomb both Khan Younis and Rafah, saying homes were hit in the areas Saturday night.

"They’re telling us to move there, and then they are bombing the houses there without warning people," Herzallah said.

The military conflict between Israel and Hamas is ongoing, making identifying departure options for U.S. citizens complex, the U.S. Embassy said.  

Embassy officials encouraged U.S. citizens to complete a crisis intake form to provide contact information "should we need to reach out to you on short notice."

-ABC News' Clark Bentson

A Gaza resident said Hamas fighters were attempting to slow the evacuation of northern Gaza, using measures that included stealing car keys, Israel's military said.

"They are preventing people from leaving," the Gaza resident told an Israeli military officer in a phone call, the audio of which was somewhat garbled and which was recorded, translated and released by the Israeli Defense Forces. The audio appeared to be a clip of a longer conversation.

The man, whom IDF identified only as a resident of Jabalya, in northern Gaza, said Hamas has been "taking the ID card and the car keys" of some locals. Israel has ordered some 1.1 million people in northern Gaza to evacuate immediately ahead of an expected ground invasion.

"You mean the movement? Hamas?" a person identified as an IDF officer said in the recording. "Who is stopping you? Hamas?"

"Yes, yes," the Gaza resident replied.

2:02

Desperate race to escape Gaza

Thousands are leaving Gaza and heading south toward the Egyptian border, hoping to reach safety before an expected Israeli ground offensive.

Chinese Foreign Minister Wang Yi told a Saudi official that Israel's "behavior has gone beyond the scope of self-defense."

He called for a stop to the "collective punishment of the people of the Gaza" during a call with Saudi Foreign Minister Prince Faisal bin Farhan, according to China's official readout of the call.

"Israel's behavior has gone beyond the scope of self-defense, and it should carefully listen to the appeals of the international community and the United Nations secretary-general to stop the collective punishment of the people in Gaza," he said.

-ABC News' Karson Yiu

U.S. nationals in Israel were being directed to board a ship scheduled to leave Israel on Monday morning.

The hourlong boarding in Haifa, a port city in northern Israel, is expected to begin at 8 a.m., officials at the U.S. Embassy in Israel said in an alert on Sunday morning.

“Boarding will proceed in order of arrival and is on a space limited basis,” the alert said.