A Palestinian patient who was amputated walks inside a hospital in the southern Gaza city of Rafah on Sunday.

GAZA STRIP — Israel on Monday called on civilians to evacuate parts of Rafah, the southern Gaza Strip city where more than a million Palestinians have been sheltering.

Instructed by Arabic text messages, telephone calls and flyers to move to what the Israeli military called an "expanded humanitarian zone" 20 kilometers away, some Palestinian families began leaving under chilly spring rain, witnesses said.

Israel's military said it had begun encouraging residents of Rafah to evacuate in a "limited scope" operation. It gave no specific reasons, nor did it say if any offensive action might follow.

Hamas official Sami Abu Zuhri said on Monday that the evacuation order ahead of an expected offensive is a "dangerous escalation that will have consequences".

Seven months into its fighting against Hamas, Israel has been threatening to launch incursions in Rafah. Victory is impossible without taking Rafah, the Israeli military said.

Israeli broadcaster Army Radio said evacuations were focused on a few peripheral districts of Rafah, from which evacuees would be directed to tent cities in nearby Khan Younis and Al Muwassi.

Many residents in Rafah said they had received telephone calls to evacuate their homes in the targeted area, in line with the announcement.

The prospect of a high-casualty operation worries Western powers and neighboring Egypt, which is trying to mediate a new round of truce talks between Israel and Hamas under which the Palestinian group might free some hostages.

Hamas' delegation will return to Egypt's capital Cairo on Tuesday to deliver the movement's "final response" to the Egyptian proposal, a Palestinian source told Xinhua News Agency on Sunday.