The 10-month-old baby held hostage in Gaza has been killed, according to Hamas, as Israel’s prime minister vowed to return to all-out war.

Kfir Bibas was taken hostage on Oct 7 alongside his brother, mother and father - Hostages and Missing Families.

Kfir Bibas, the youngest person to be taken hostage, died in captivity alongside his four-year-old brother Ariel and their mother Shira, Hamas said in a statement.

The Israel Defense Forces (IDF) said it was investigating the claims and was in touch with the surviving family.

In a video statement, Benjamin Netanyahu, the Israeli prime minister, said there had been questions over whether Israel would return to war after “this phase of returning our abductees is exhausted”.

On Wednesday, Joe Biden called on Israel to show restraint. “To continue down the path of terror, violence, killing and war is to give Hamas what they seek,” the US president warned. “We can’t do that.”

Welcoming the release of the hostages, Mr Biden did not address the possible ceasefire extension but said he “remain[s] determined to secure the release of every person taken hostage by Hamas during its brutal terrorist assault on Israel”.

“The deal to pause the fighting in Gaza and facilitate the release of hostages — a deal the United States worked intensively to secure, sustain, and extend — is now in its sixth day,” he said. “This deal has delivered meaningful results.”

But Mr Netanyahu promised to continue fighting at the nearest opportunity, as the IDF said it had completed plans for the next phase of combat in south Gaza.

He said: “There is no way we are not going back to fighting until the end. This is my policy, the entire cabinet stands behind it, the soldiers stand behind it, the people stand behind it.”

It came as the Israel Defense Forces said 10 Israeli hostages and four Thai nationals had been released by Hamas on Wednesday night in the sixth tranche of the temporary ceasefire deal.

Two dual Israeli-Russian nationals were freed earlier on Wednesday.

There were hopes that the current truce could be extended past its expiry on Thursday morning, with Qatari mediators reportedly expressing “confidence” of further swaps.

With the IDF investigating reports of the Bibas killings, Benny Gantz, a war cabinet minister, warned the news could be  seen as “psychological warfare from Hamas”.

Kfir, his brother and mother were abducted in the Kibbutz of Nir Oz on Oct 7 along with their father, Yarden, 34.

An IDF spokesman said on Tuesday that the family was no longer in the control of Hamas and had been handed over to a different terror group, which was holding them in Khan Younis.

Hamas said the children and their mother had been killed in an Israeli airstrike, without providing evidence.

The Bibas family requested privacy in a statement and said they were “waiting for the [claims of the killings] to be confirmed and hopefully rebutted by military officials”.

Jimmy Miller, a cousin of Shira Bibas, said: “Hamas abducted them alive. Hamas is solely responsible for their well-being. Hamas must return them to us alive.”

“We’re not interested in whether they transferred them to somebody else or to some other group.”

Israel believes Hamas still has enough women and children hostages to allow the current pause in fighting in Gaza to be extended by another two to three days, an official involved in the negotiating process said on Wednesday. Israel has said it will extend the truce by one day for every 10 hostages freed.

“We know for a fact that there are additional hostages in the hands of Hamas for at least two more days, potentially three days from the list of women and children,” said the official, who spoke on condition that he not be named.

The official added that “follow-on agreements”, for the men held by Hamas, would only be negotiated after the release of all the women and children.

Families beg for return of male hostages

It came as the families of male Israeli hostages issued an emotional plea for their release on a visit to London.

Orit Meir’s son, 21-year-old Almog, was snatched from the SuperNova music festival, where hundreds were massacred.

The 61-year-old said she only knows he is alive through a video released by Hamas shortly after his capture.

“I just want him back,” she told The Telegraph, with tears in her eyes.

“It doesn’t matter if your child is 10, 21 or 40. It’s still your child and you yearn for them like they were a baby.”

“I’m happy for the families who have been reunited. But I want my baby back, 54 days is too much.”

Ilay David, brother of 26-year-old Evyatar, said was aware of the difficulty in securing the release of male hostages.

Evyatar was also kidnapped at the music festival and similarly appeared in a video, looking terrified.

“He’s a young man, which probably means Hamas has written him [down] as a soldier, which he is not,” said Ilay.

“And that’s so upsetting that he’s the last one in the food chain, although he has done  nothing to harm anyone. The only crime he committed was to celebrate in a festival alongside so many others that were just living their lives.”

Division over length of truce

Antony Blinken, the US secretary of state, who was scheduled to travel to Israel on Thursday, said the administration wanted the truce to continue because it “means that more hostages will be coming home, more assistance will be getting in”.

However, Itamar Ben Gvir, the hard-Right security minister and a key partner in Mr Netanyahu’s coalition, threatened to bring down the government if the war in Gaza ends.

“Stopping the war equals breaking apart the government,” he said in a statement. Mr Ben Gvir’s departure would leave Mr Netanyahu with a very slim majority to keep his hold on power.

It came as Antonio Guterres, the UN secretary general, said reports of sexual violence during the Hamas rampage must be investigated, as he warned of an “epic humanitarian disaster” in Gaza.

Mr Guterres said there were numerous accounts of sexual violence during the “abhorrent acts of terror by Hamas on October 7” which saw thousands injured, more than 1,200 people killed and about 240 people abducted.

Speaking of the remaining hostages being held in Gaza, Mr Guterres said that all of them “must be released immediately and unconditionally”.

“Until then,” he added, “they must be treated humanely and (humanitarian organisation) the ICRC must be allowed to visit them.”

There were further tensions in the West Bank on Wednesday, as the IDF said it fired on armed terrorists in a refugee camp in Jenin, killing two men.

Israel’s military also reported it had killed a Palestinian Islamic Jihad commander in the West Bank as violence continues to soar in the occupied territory amid the war in Gaza.

Muhammad Zubeidi was “eliminated” by IDF fighters in the Jenin refugee camp, the IDF said. He was accused of several shooting attacks in the area.

Meanwhile, an 85-year-old hostage released by Hamas in October said she told Yahya Sinwar, the Hamas chief, that he should be “ashamed of himself” when they met.

Yocheved Lifshitz, a lifelong peace activist, said Sinwar visited her three or four days into captivity.

She told Hebrew-language newspaper Davar: “I asked him how he is not ashamed to do such a thing to people who have supported peace all these years.

“He didn’t answer. He was silent.”