Israel says it has informed the families of 31 people held in the territory since 7 October that their relatives are dead. The news comes as the Qatari prime minister says Hamas has given a “generally positive” response to proposals for a deal trading a break in the fighting and release of Palestinian prisoners for the return of more hostages.

The number of the dead is more than a fifth of the remaining 136 hostages being held by in Gaza, according to available intelligence collated by the Israeli military, and comes amid pressure on Benjamin Netanyahu’s governmentover its handling of the hostage crisis.

Mohammed bin Abdulrahman Al Thani, whose country is acting as a mediator between the two sides, said on Tuesday that Hamas’s response to proposals drawn up by the US and Israel and tabled more than a week ago “inspires optimism”, but said he would not go into details.

The US secretary of state, Antony Blinken, speaking with the Qatari PM on his fifth tour of the region since the 7 October attacks, said he would discuss Hamas’s response with Israel on Wednesday. “There’s still a lot of work to do be done, but we continue to believe that an agreement is possible, and indeed essential,” he said. “We will continue to use all means available to us to reach an extended truce during which the hostages will be released from Gaza. Reaching an agreement on hostages is the best path forward for an expanded truce.”

A statement from Hamas referred to “a comprehensive and complete ceasefire, ending the aggression against our people”. Israel has previously ruled out a permanent ceasefire and it is believed was proposing a pause in the fighting of 40 days.

The kernel of the negotiations turns on whether there are guarantees, implicit or explicit, that an extended ceasefire will become permanent, and whether the number of Palestinian prisoners likely to be released meets the demands of Hamas for a near emptying of jails. The future status and presence of Israeli forces inside Gaza during the ceasefire has also been contentious.

The revelation that 31 hostages have died first emerged from a confidential internal Israeli review leaked to the New York Times. The fate of a further 20 people is also in question, amid unconfirmed intelligence they may also have died during their captivity, the report said.

The figure was later confirmed by the Hostage and Missing Families Forum, which represents families of the captives. “According to the official data we have, there are 31 victims,” it said in a statement.

The disclosure that so many of the remaining hostages are dead, a higher number than previously disclosed, seems certain to intensify scrutiny of the Netanyahu government’s controversial handling of the crisis, which has provoked fury among many hostage families.

While about half of those taken captive during the attack were released last year after a hostages-for-ceasefire deal, in which Palestinian prisoners being held in Israeli jails were also freed, negotiations for a second deal have dragged on for weeks.

The circumstances of the hostages’ deaths remained unclear, with the Israeli authorities suggesting that many of those deaths had occurred on 7 October during Hamas’s incursion into southern Israel, in which 1,200 people were killed.

The issue has been complicated by the piecemeal emergence of information about those taken hostage on 7 October in the intervening months, with the families of some of those who had been understood to have been taken alive being later told they had been killed.

It is not known if the Israel Defense Forces review meant that Hamas was holding the bodies of all of those understood to be dead in order to bargain with them in the future.

Under the continuing negotiations for a second, lengthy ceasefire, being mediated by Qatar and Egypt, women, sick people, children and elderly captives would be released in exchange for Palestinian prisoners, with bodies expected to be exchanged later if the first phase was successful.

More than 240 hostages were initially believed captured by Hamas last October, but the precise number has been constantly adjusted.

While senior Israeli officials have said one of the goals of the war was to secure the release of hostages through military pressure, Hamas has said on several occasions that hostages have died during Israeli strikes, claims that have not been independently verified.

However, during the course of a conflict that has killed more than 27,000 Palestinians in Gaza, the IDF has so far rescued only one hostage, while three others, men who had escaped their captors in northern Gaza, were killed by Israeli soldiers as they approached an Israeli position.

Blinken’s visit also comes amid growing concerns in Egypt about Israel’s stated intentions to expand the combat in Gaza to areas on the Egyptian border that are crammed with displaced Palestinians.

It was also disclosed that the Israeli military had begun investigating dozens of incidents where Israeli soldiers may have broken the IDF’s own rules of conduct or violated international law governing conflict, mostly in incidents involving significant civilian casualties or the destruction of civilian infrastructure.

Israel’s defence minister has said Israel’s offensive would reach the town of Rafah, on the Egyptian border, where more than half of Gaza’s 2.3 million people have sought refuge and are now living in increasingly miserable conditions.

UN humanitarian monitors said on Tuesday that Israeli evacuation orders now covered two-thirds of Gaza, driving thousands more people every day towards the border areas.

Egypt has warned that an Israeli deployment along the border would threaten the peace treaty the two countries signed more than four decades ago.

Egypt fears an expansion of combat to the Rafah area could push terrified Palestinian civilians across the border, a scenario it says it is determined to prevent.