The remains of an Israeli citizen thought to be kidnapped by the militant group Hamas were identified overnight, ABC News has learned.

The Israeli Prime Minister's Office announced Friday morning that the number of hostages currently held captive by Hamas in the Gaza Strip is 137, down from 138.

Be'eri, a kibbutz in southern Israel near the border with Gaza, confirmed Friday morning the death of one of its residents, Dror Kaplun, who was initially believed to be a hostage but was actually killed in the Oct. 7 terror attack. His wife, Dr. Marcel Freilich Kaplun, was also killed in the attack, according to the kibbutz.

-ABC News' Anna Brund, Jordana Miller and Morgan Winsor

Photos and video circulating online Thursday show dozens of Palestinian men being detained by the Israeli military, many stripped down to their underwear, in the streets of a city in northern Gaza.

In one of the images, dozens of men are lined up against a wall while kneeling with their hands behind their backs and stripped down to their underwear. The same image shows dozens of other men in an Israel Defense Forces truck. ABC News geolocated a sign for a pharmacy captured in the image to the city of Beit Lahia in northern Gaza.

A video of the same scene shows a long line of men in their underwear sitting and standing in a line, surrounded by IDF personnel.

When asked about the images and video, the IDF told ABC News that its troops "apprehended hundreds of terror suspects" in Shejaiya, Jabalya and Khan Yunis.

Hamas said in a statement in response to the images that the men were unarmed civilians.

Hani Almadhoun, director of philanthropy for the United Nations Relief and Works Agency, told ABC News that several of his family members were detained by the IDF, including his 72-year-old father, brother and 13-year-old nephew.

"They just want the job to feed to provide for their families to make a buck here and there live in a nicer home. That's all not happening now for them," he said. "Now they've been dubbed as operatives and combatants when they were napping in their homes in the safety of their homes with their kids."

Almadhoun, who is based in D.C., said he hasn’t heard from them since and doesn't know how to go about finding information on their whereabouts.

-ABC News' Emmanuelle Saliba, Kerem Inal, Layla Ferris, Helena Skinner and Victoria Beaule

A senior Hamas official in Lebanon warned Thursday that the chances of another hostage release are "dwindling" and that the detainees will not be returned until "the aggression stops."

"The chances of their return diminish with the length of the aggression, and their impact may be lost forever," the official, Osama Hamdan, said in a statement. "The possibilities of their return are dwindling as the aggression goes on and maybe there will be no trace of them forever."

Nearly 140 hostages are believed to still be held by Hamas, according to the Israel Defense Forces.

During President Joe Biden's call Thursday with Israeli Prime Minister Benjamin Netanyahu, the president noted that "it was Hamas’s refusal to release young women civilian hostages that led to" the end of the multiday cease-fire, according to a White House readout of the leaders' call.

Biden "reiterated that the [International Committee of the Red Cross] must be permitted to access remaining hostages held by Hamas terrorists," the White House said, and Biden and Netanyahu "agreed to remain deeply engaged to pursue every possible opportunity to free the remaining hostages."

Biden also stressed the importance of humanitarian aid into Gaza. Biden "welcomed the recent Israeli decision to ensure that fuel levels will meet requisite needs, but stressed that much more assistance was urgently required across the board," the White House said.

Biden again noted the need to separate civilians in Gaza from Hamas, the White House said, and the president reiterated his concern about the "extremist violence committed against Palestinians and the need to increase stability in the West Bank."

-ABC News' Fritz Farrow