Hamas said it would begin releasing Israeli hostages in Gaza on Monday morning, before U.S. President Donald Trump chairs an international summit in Egypt on his peace plan for the region.

As part of the deal's first phase, Hamas will free the captives, 20 of whom Israel believes are still alive, in exchange for nearly 2,000 Palestinian prisoners.

"According to the signed agreement, the prisoner exchange is set to begin on Monday morning as agreed," Hamas official Osama Hamdan told AFP in an interview Saturday.

Trump and Egyptian President Abdel Fattah al-Sisi will then chair a summit of more than 20 countries in the Red Sea resort of Sharm el-Sheikh on Monday afternoon, the Egyptian presidency announced.

The meeting will aim "to end the war in the Gaza Strip, enhance efforts to achieve peace and stability in the Middle East, and usher in a new era of regional security and stability," it said.

UN Secretary-General Antonio Guterres will attend the summit, as will Britain's Prime Minister Keir Starmer, his counterparts from Italy and Spain, Giorgia Meloni and Pedro Sanchez, and French President Emmanuel Macron.

There was no immediate word on whether Israel's Prime Minister, Benjamin Netanyahu, would be there. Meanwhile, Hamas said it would not take part, as it had "acted principally through... Qatari and Egyptian mediators" during talks, Hamas political bureau member Hossam Badran said.

Despite the apparent breakthrough, mediators still have the tricky task of securing a longer-term political solution that will see Hamas hand in weapons and step aside from governing Gaza.

Under the Trump plan, as Israel conducts a phased withdrawal from Gaza's cities, it will be replaced by a multinational force from Egypt, Qatar, Türkiye and the United Arab Emirates, coordinated by a U.S.-led command center in Israel.

On Saturday, U.S. Central Command (CENTCOM) chief Admiral Brad Cooper, Trump's Middle East envoy Steve Witkoff and Trump's son-in-law Jared Kushner visited Gaza, where hundreds of thousands of Palestinians were again on the move, returning to their devastated homes.

Witkoff, Kushner and Trump's daughter Ivanka then went on to Tel Aviv to attend a gathering with the families of the remaining Israeli hostages held in Gaza.

Hamas has until noon on Monday to hand over 47 remaining hostages, living and dead, from the 251 abducted in the attack two years ago. 

In exchange, Israel will release 250 prisoners, including some serving life sentences for deadly anti-Israeli attacks, and 1,700 Gazans detained by the military since the war broke out.

The Israeli prison service on Saturday said it had moved the 250 national security detainees to two prisons ahead of the handover. 

More than 500,000 Palestinians had returned to Gaza City by Saturday evening, according to Gaza's civil defence agency, a rescue service operating under Hamas authority.

The UN's humanitarian office says Israel has allowed agencies to start transporting 170,000 tonnes of aid into Gaza if the ceasefire holds.

(With input from agencies)