Bullets were found in the bodies of the six Israeli hostages retrieved from Gaza this week, the Israeli military and the Hostage Families Forum campaign group said on Thursday.
The military told Reuters it retrieved another four bodies alongside its hostages, presumed to be Hamas militants, and that those bodies did not show signs of bullet wounds.
The comments came a day after US President Joe Biden pressed Israeli Prime Minister Benjamin Netanyahu on the urgency of sealing a deal for a truce between Israel and Hamas in Gaza and the release of hostages held by Palestinian militants there.
A total of 109 hostages are believed to remain in Gaza. About a third of them are thought to be dead, with the fate of the others unknown.
"In every minute that the deal is not completed, another hostage could lose their life. It is clear to all that the return of the hostages is only possible through a deal," the campaign group said.
It said the recovery of six hostage bodies was no achievement but rather a testament to the government's failure to reach a deal on time and return the hostages alive.
Internationally mediated ceasefire talks resumed in Cairo earlier on Thursday. US Secretary of State Antony Blinken left the region on Tuesday without producing a breakthrough to end the 10-month-old war.
Months of on-off ceasefire talks have circled the same issues, but Israel and the Palestinian militant group Hamas have stuck firmly to their demands.
Most of Israel's hostages were seized by Hamas gunmen who rampaged through southern Israel on 7 October, 2023, killing some 1200 Israelis and foreigners and abducting around 250 as hostages.
Since 7 October, Israel's military has levelled Gaza, driving nearly all of its inhabitants from their homes and killing at least 40,000, according to Palestinian health authorities. Israel says it has killed some 17,000 militants.
Reuters