Israeli aircraft on Monday began dropping flyers in eastern Rafah, warning thousands of people sheltering in the city that they may be in danger ahead of a possible Israeli operation.

"The IDF will be operating against the terrorist organizations in the area where you are located, as it has operated until now," the flyers read in Arabic, according to a translation provided by the Israel Defense Forces. "Anyone found near terrorist organisations endangers themselves and their family members."

The flyers included directions for an evacuation, including information about the humanitarian area near Al-Mawasi, Israel said.

-ABC News' Joe Simonetti and Kevin Shalvey

The U.N. Agency for Palestine Refugees said Monday it wouldn't begin to evacuate its staff from Rafah, adding that a possible Israeli invasion into the refugee city would be "devastating."

"UNRWA is not evacuating: the Agency will maintain a presence in Rafah as long as possible & will continue providing lifesaving aid to people," the group said in a statement.

An invasion into the city "would mean more civilian suffering & deaths," the agency said.

-ABC News' Kevin Shalvey

Israeli military officials on Monday issued a warning to civilians in eastern Rafah to begin a "gradual movement" to a humanitarian area.

"Calls to temporarily move to the humanitarian area will be conveyed through flyers, SMS messages, phone calls and media broadcasts in Arabic," Israel Defense Forces officials said in a statement posted to social media.

Israel said a humanitarian area around Al-Mawasi, a coastal town, had been expanded "to accommodate the increased levels of aid flowing into Gaza." That aid included new field hospitals and additional food and water, IDF officials said.

Prime Minister Benjamin Netanyahu had said last week that Israel would call for an evacuation of civilians prior to beginning its planned invasion into the southern Gaza city. Israeli officials haven't yet detailed a timeline for the expected operation.

"The IDF will continue pursuing Hamas everywhere in Gaza until all the hostages that they're holding in captivity are back home," IDF officials said Monday.

-ABC News' Kevin Shalvey

Hamas said Sunday that negotiations in Cairo have concluded and that its delegation will leave Cairo tonight.

Hamas says negotiations with Israel for a permanent cease-fire have fallen through after Israel rejected its proposals, including demands for a permanent cease-fire, complete withdrawal of Israel's forces from Gaza, the return of displaced people and a prisoner exchange.

"Israel's rejection of the mediators' proposal, through the amendments it made to it, has brought things back to square one," Hamas said in a statement Friday.

Hamas said Israel bears "the full responsibility" for the failure to reach an agreement.

"The enemy's army's attack on Rafah and the direct occupation of the crossing immediately after Hamas announced its agreement to the mediators' proposal confirms that the occupation is evading reaching an agreement. Netanyahu and his extremist government are using negotiations as a cover for the attack on Rafah and the occupation of the crossing, and continuing the genocide against our people," Hamas said.