By Israel’s military says it has begun ordering Palestinians to leave parts of eastern Rafah ahead of a “limited” operation in the southern Gaza city.
About 100,000 people are being directed to head for an “expanded humanitarian area” in Khan Younis and al-Mawasi.
After seven months of war, Israel says it must take Rafah to defeat Hamas.
But the UN and US warn that an assault on the city, where more than a million displaced Palestinians are sheltering, could have catastrophic consequences.
A senior Hamas official, Sami Abu Zuhri, told the Reuters news agency that the Israeli order was “a dangerous escalation that will have consequences”.
Israeli air strikes in Rafah reportedly killed at least 19 Palestinians overnight, after rockets launched from the area by Hamas fighters killed four Israeli soldiers at the nearby Kerem Shalom border crossing – the key entry point for humanitarian aid into Gaza. The crossing was closed following the attack.
There have also been reports of Israeli attacks on Rafah, hours after the evacuation order was issued.
Meanwhile, the latest efforts for a new ceasefire and hostage release deal have stalled, with both Israel and Hamas saying they would not give ground on key demands. Hamas wants a permanent end to the war, which Israeli Prime Minister Benjamin Netanyahu says he cannot accept.
Mediators said they were continuing their efforts.
In an initial briefing to journalists on Monday morning, Israel Defense Forces (IDF) spokesman Lt Col Nadav Shoshani stressed that the operation planned in Rafah was of “limited scope”.
He said that no timeframe had been announced and that the evacuation affecting an estimated 100,000 people would be carried out in “a gradual way”.
The IDF is using text messages, flyers and social media to tell people to move.
One of the Arabic flyers dropped by aircraft features a map that identifies nine area blocks in south-eastern Rafah, where the IDF says it will “be operating against the terrorist organisations”. They include al-Shuka, al-Salam, al-Janina and al-Yarmouk, as well as farmland near Kerem Shalom.
The flyer instructs residents of those areas to evacuate immediately and head towards an area stretching north along the Mediterranean coast from al-Mawasi – a thin strip of agricultural land that has long been an IDF-designated “humanitarian zone” – to Khan Younis and the central town of Deir al-Balah.
The IDF said the expanded humanitarian area included “field hospitals, tents and increased amounts of food, water, medication and additional supplies”.
“An ongoing situation assessment will guide the gradual movement of civilians in the specified areas, to the humanitarian area,” it added.
Such messages are unlikely to allay the fears of those living in the city that a wider offensive is on the cards.
The UN agency for Palestinian refugees, UNRWA, which runs the largest humanitarian organisation in Gaza, said the “consequences would be devastating for 1.4 million people” in Rafah.
