Dozens of distraught Israeli families scrambled for information on missing loved ones Sunday, a day after Palestinian militants unleashed a surprise attack and forced hostages, some of them bloodied, back to Gaza.
More than 100 Israelis have been taken hostage, the government's press office said.
"I just want to be able to hug him," said Omri Shtivi, 30, whose brother Idan went missing after a desert rave near the Gaza border came under attack by Hamas militants.
Speaking to AFP by telephone, Shtivi said the authorities had not contacted the family to provide information or offer help in finding his brother.
Police and the army's Home Front Command opened late Saturday -- about 16 hours after fighting began -- a "command centre for missing persons" near Ben Gurion International Airport close to Lod in central Israel.
Mor Strikovski, 42, arrived there on Sunday to report her missing mother, a 63-year-old resident of Kibbutz Beeri, who she believes is being held in Gaza.
"Yesterday, it was a really tough day," Strikovski told AFP, recalling that Hamas fighters on Saturday killed several residents of Beeri and held dozens hostage before an overnight rescue operation by Israeli special forces.
"Today, I received a video (showing) that she was kidnapped," she said. "My cousin... saw it on Telegram and asked me if I recognise her."
Hamas "kidnapped her in her house with her husband and two neighbours," according to Strikovski.
"We guess they are in Gaza, so I am here to report it," she said, expressing hope the militants "will treat her well and that she will return safe."
- 'Played dead' -
Dozens of families arriving at the command centre Sunday were welcomed by social workers, before sharing with police officers any information they may have of their relatives, AFP correspondents said.
They were asked to provide personal items from which DNA samples can be extracted, like toothbrushes, shaving razors or used clothes.
At a nearby forensic lab, the samples are corroborated against a database with DNA extracted from dead bodies.
But with hundreds of confirmed deaths and dozens still unaccounted for, the process may take a long time, Shelly Harush, the police commander overseeing the operation, told reporters, urging patience.
Leaving the command centre, some people wept and embraced each other. Visibly shaken and exhausted, many refused to speak to the media.
Residents of the neighbouring city of Lod were waiting outside to offer drinks and food for the families, the AFP correspondents said.
Ester Borochov, 19, who survived the rave attack, told Israel's Channel 12 that "they (Hamas militants) started shooting at us at point blank" but she managed to flee in her car before it was hit by bullets and broke down.
"A young man took us in his Jeep. They shot him, he lost consciousness and his car overturned," she said.
"We played dead, me and my friend, for two-and-a-half hours... before help arrived," Borochov said.
"That's how we survived."
The pain of the missing was felt outside Israel, too.
The mother of German-Israeli woman Shani Louk, 22, who attended the rave party, appealed for help finding her after identifying Louk in a video showing militants in Gaza.
Israel's ambassador to Britain said a British national "is in Gaza." She did not identify the man or confirm if he was kidnapped, but the mother of Jake Marlowe, 26, said he had been providing security at the rave.
- 'Worst nightmares' -
A video purportedly from Gaza showing Nir Oz resident Shiri Bivas along with her nine-month-old baby Kfir and three-year-old son Ariel, was "the only confirmation we have" of their situation, said Bivas's cousin, Yifat Zilber.
"All the information we have is primarily from social media," Zilber, 37, told AFP by telephone.
"We have no idea what happened to her (Bivas's) husband, Yarden" and parents, who Zilber said were "probably kidnapped" too but do not appear in the video.
"We want them to return safe," Zilber said, her voice cracking.
"They're innocent civilians. There are international bodies that are meant to safeguard innocent civilians... They need to intervene."
Adva Adar has similarly learned from a video circulating on social media that her grandmother, 85-year-old Yaffa Adar also from Nir Oz, was kidnapped.
"Yesterday at about 8:00 (0500 GMT) we lost contact with her," the granddaughter told reporters via video conference.
When army forces finally reached the house at around 5:00 pm, it was "totally broken, burned to ashes, and she wasn't there", said Adva Adar.
"I can't imagine how scared, how uncomfortable she is. She's 85, sick, without her medicine. We don't know where she is or if she has food or water."
Adva Adar, too, said "we haven't heard anything yet" from the authorities.
"Not even in our worst nightmares did we imagine this."
