Arab leaders gathered in Saudi Arabia on Friday for a meeting that focused on Cairo's proposed plan to rebuild Gaza to counter US President Donald Trump's controversial scheme for the United States to take over the enclave and to save a fragile cease-fire between the Palestinian militant group Hamas and Israel after 16 months of conflict.

However, hours after Hamas released the bodies of four hostages in the first such handover, Israel's military said early on Friday that one of the four was not that of Shiri Bibas, describing the remains as "anonymous" and demanding Hamas return the correct body. Hamas said all the four returned on Thursday were killed in Israeli airstrikes, but Israel said testing had found that two boys and 83-year-old Oded Lifshitz were killed by their captors.

Israeli Prime Minister Benjamin Netanyahu accused Hamas on Friday of committing a "cruel and evil" violation of the Gaza cease-fire deal by failing to return the captive Shiri Bibas.

"We will act with determination to bring Shiri home, along with all of our captives, both the living and the fallen, and ensure that Hamas pays the full price for this cruel and evil violation of the agreement," Netanyahu said in a video statement.

Hamas said on Friday the remains of Israeli hostage Shiri Bibas appear to have been mixed with other human remains from the rubble after an Israeli airstrike hit the place where she was held.

On Thursday, Palestinian militants handed over four black coffins in a public display as a crowd of Palestinians and militants watched, creating a spectacle that was condemned by United Nations chief Antonio Guterres as "abhorrent and appalling".

In another potential blow to the deal, Netanyahu has ordered an intensification of military operations in the occupied West Bank after three parked buses exploded in Bat Yam, near Tel Aviv, without casualties and with no claim of responsibility.

Some parts of the West Bank were immediately sealed off and further restrictions have been imposed on the movement of Palestinians.

Israeli political analyst Akiva Eldar said the attacks have "paralyzed public transportation" in the area on a busy day, Al Jazeera reported. "There is (an) escalation in the West Bank and now what we are watching is that Tel Aviv is not safe," he said.

Arab states have been scrambling to formulate an alternative to Trump's proposal to permanently remove Gaza's 2.3 million population and transform the enclave into the "Riviera of the Middle East", which has provoked widespread outrage.

Disagreements remain

However, disagreements remain over who should govern the Palestinian territory and how to fund its reconstruction, media reported.

The official Saudi Press Agency reported on Thursday that Egypt and Jordan were participating in the meeting along with the other five members of the Gulf Cooperation Council — the United Arab Emirates, Kuwait, Qatar, Oman and Bahrain. It also said decisions issued by the "unofficial fraternal meeting" would appear on the agenda of an emergency Arab League summit in Egypt on March 4.

Egyptian President Abdel Fattah El-Sisi arrived in Saudi Arabia on Thursday. Palestinian President Mahmoud Abbas has also been invited, media reported.

Umer Karim, an expert on Saudi foreign policy, called the Riyadh meeting the "most consequential" in decades for the wider Arab world and the Palestinian issue.

Gaza is largely in ruins after more than a year of conflict, with the UN recently estimating that rebuilding will cost more than $53 billion.

Egypt has yet to announce its initiative, but it expects to finalize the plan "by next week", while its first phase should begin "after the emergency Arab summit in Cairo", Egyptian state media said.

According to the Qatari newspaper The New Arab, Egypt is advancing a two-stage plan that is expected to last 10 years and focus on reconstruction, development and infrastructure projects, while preparing for a broader long-term solution to the Palestinian issue. The plan envisions a redistribution of residential areas, reducing population density in northern Gaza and establishing low-population "safe zones" near Israeli border communities.

An Arab diplomat familiar with Gulf affairs told Agence France-Presse: "The biggest challenge facing the Egyptian plan is how to finance it."

Agencies and Xinhua contributed to this story.