TEL AVIV, Israel - Israel was eagerly awaiting what one official called the "miracle" release Friday of women and children taken hostage by Palestinian militants during the deadliest attack in the country's history.

But the authorities were also gearing up for the complex task of helping those returning home from a nearly seven-week hostage ordeal that may have left them deeply traumatised.

Hamas militants stormed into southern Israel on October 7, killing about 1,200 people, most of them civilians, according to an Israeli count, and seizing about 240 hostages.

Israel has vowed to "crush" Hamas in response and unleashed a withering military campaign that Gaza's Hamas government says has killed nearly 15,000 people in the coastal territory.

On Friday a first tranche of around a dozen women and children hostages were expected to be sent back to Israel in an exchange that would begin at 4:00 pm (1400 GMT).

Israel is set to release three times as many Palestinian prisoners from Israeli jails -- women and teenage boys -- under the terms of the deal reach with Gaza's Hamas rulers.

"We hope the picture will be beautiful at the end of the day," Ziv Agmon, legal adviser to Prime Minister Benjamin Netanyahu's office, told reporters, saying Israel would "follow the agreement" but could not speak for Hamas.

"With a terrorist organisation like Hamas, everything that happens in the coming days is a miracle," he said.

Over the course of the four-day truce, which began at 07:00 am, at least 50 hostages are expected to be freed, with 150 Palestinians prisoners to be released in exchange.

Agmon said the hostages would be received individually or in groups by the International Committee of the Red Cross and taken across the border and handed to soldiers who would "meet each hostage and identify them physically... to see that these are the correct people".

Doctors would perform a "full physical examination" of every hostage, and they would be able to video call telephone family members in a conversation monitored by professionals.

'Life has changed dramatically'

"This is very important... because we don't know what they know. Many have family members who are not alive anymore, there are children with parents that were murdered, siblings who were also murdered," he said.

The released hostages would then be flown to five major hospitals and medical facilities around Israel, where they would be physically reunited with their loved ones.

Experts said it was crucial that they be slowly and gentle reintroduced to reality.

"The biggest risk is to usher them into their previous life without doing it slowly and gently because it's overwhelming and some of them will shut down completely," Dr Rony Berger, a senior clinical psychologist and expert on coping with the trauma of a terror attack or major disaster.

The first thing was to protect them from "the carnival" of their homecoming, he told AFP.

"They were probably isolated so bringing them into all this stimulation is very hard," he said, explaining they would be taken to a "secluded place with very few family members".

"They've been instructed not to shower them with love and toys, just bring one thing that reminds him of the past and very slowly to re-enter them into reality," he told AFP.

"Life has changed dramatically. It will take time for them to reconnect to their life before," he said, adding many would also learn that one or both parents had been killed, or other close relatives.

"Obviously you don't tell a three-year-old in the same way (as an older child) but they may ask and you have to tell them something. And if he's six-years-old, you have to tell him. So mourning will be part of that," he said.

"It's going to be very difficult for them. They don't have their kibbutz, they don't have their friends."