"Hannibal at Erez, dispatch a Zik [attack drone]," came the command on October 7.

Those words, reported by Israeli newspaper Haaretz in July, confirm what many Israelis have feared since the Hamas attacks on October 7 in southern Israel.

Israeli forces have killed their own citizens.

Israeli authorities say more than 800 civilians and around 300 soldiers were killed on October 7.

A number of Israeli hostages have since died in Gaza.

Israelis are still reeling from the horror and pain of the Hamas-led terror attack, which was the bloodiest single day in Israel's history.

But the Israeli military is coming under increasing pressure to reveal just how many of their own citizens were killed by Israeli soldiers, pilots and police in the confusion of the Hamas attack on southern Israeli communities.

Survivors and relatives have been asking not just "what went wrong", but whether the military invoked the controversial — and supposedly rescinded — "Hannibal Directive".

What is the Hannibal Directive?

The Israel Defense Forces (IDF) said the directive was named at random by a computer program, but Hannibal was the famous Carthaginian general who took poison rather than be captured by the Romans.

The doctrine, written in 1986 in response to the kidnapping of Israeli soldiers in Lebanon, gave permission for Israeli forces to fire on enemies holding their comrades hostage — even at risk to those hostages.

Its authors said the directive did not allow captives to be killed, but critics say that over time an interpretation spread through the military that it was better to kill comrades than to allow their capture.

"They interpreted it as if they are [meant] to intentionally, deliberately kill the soldier in order to foil the attempted abduction, and that was wrong," Israeli philosopher Asa Kasher, who wrote the IDF code of ethics, told the ABC.

"That is legally wrong and morally wrong and ethically wrong, it's wrong on all accounts."

In 2011, Hamas successfully used an Israeli hostage to secure a major prisoner exchange, swapping one Israeli soldier, tank gunner Gilad Shalit, for more than 1,000 prisoners, including the current Hamas leader, Yahya Sinwar.

After October 7, there were some testimonies from Israeli civilians and military personnel that Israeli forces responding to the Hamas attack killed their own citizens.

Nevertheless, many Israelis and supporters of Israel condemned anyone who suggested it had occurred, before more testimonies and Israeli media reports confirmed it was true.

The IDF has not confirmed or denied a version of the Hannibal directive was applied on October 7, only saying it is one of many things from that day under investigation.

In response to questions from the ABC, the Israeli military provided a statement saying: "The IDF is currently focused on eliminating the threat from the terrorist organisation Hamas."

"Questions of this kind will be looked into at a later stage."

'This was a mass Hannibal'

In July, the Israeli newspaper Haaretz revealed commanders in the IDF gave the order to fire on troops who had been captured by Hamas at three separate locations, explicitly referencing the Hannibal Directive.

One former Israeli officer, Air Force Colonel Nof Erez, told a Haaretz podcast the directive was not specifically ordered but was "apparently applied" by responding aircrews.

Panicked, operating without their normal command structure and unable to coordinate with ground forces, they fired on vehicles returning to Gaza, knowing they were likely carrying hostages.

"This was a mass Hannibal. It was tons and tons of openings in the fence, and thousands of people in every type of vehicle, some with hostages and some without," Colonel Erez said.

Air force pilots described to Yedioth Ahronot newspaper the firing of "tremendous" amounts of ammunition on October 7 at people attempting to cross the border between Gaza and Israel.

"Twenty-eight fighter helicopters shot over the course of the day all of the ammunition in their bellies, in renewed runs to rearm. We are talking about hundreds of 30-millimetre cannon mortars and Hellfire missiles," reporter Yoav Zeitoun said.

"The frequency of fire at the thousands of terrorists was enormous at the start, and only at a certain point did the pilots begin to slow their attacks and carefully choose the targets."

Tank officers have also confirmed they applied their own interpretation of the directive when firing on vehicles returning to Gaza, potentially with Israelis on board.

"My gut feeling told me that they [soldiers from another tank] could be on them," tank captain Bar Zonshein told Israel's Channel 13.

Captain Zonshein is asked: "So you might be killing them with that action? They are your soldiers."

"Right," he replied, "but I decided that this is the right decision, that it's better to stop the kidnapping, that they won't be taken."

Investigative journalist Ronen Bergman wrote for Yedioth Ahronot newspaper that the military had enacted the Hannibal Directive at midnight on October 7.

"The IDF instructed all its fighting units in practice to follow the 'Hannibal Directive', although without clearly mentioning this explicit name," he said.

"The instruction is to stop 'at all costs' any attempt by Hamas terrorists to return to Gaza, using language very similar to the original 'Hannibal Directive', despite repeated assurances by the security establishment that the procedure has been cancelled."

Bergman's investigation found 70 vehicles were destroyed by Israeli aircraft and tanks to prevent them being driven into Gaza, killing everyone inside.

"It is not clear at this point how many of the abductees were killed due to the activation of this [Hannibal] order on October 7," he wrote.

The original Hannibal Directive, while confidential, reportedly recommends small arms and sniper fire towards enemies holding hostages — and not to use bombs, missiles or tank shells.

In 2015, Israel's attorney-general said it specifically prohibited killing a hostage.

It wasn't just soldiers under fire on October 7, though.

Tank ordered to fire on house

In two incidents, Israeli civilians survived Israeli forces firing on them and killing other hostages.

One survivor of Kibbutz Nir Oz, a Gaza border community, described being fired upon by the Israeli military as Hamas members tried to take her and other hostages across the border in an electric wagon.

"[An] IDF helicopter appeared above us. At some point the helicopter shot at the terrorists, the driver and the others. There was screaming in the wagon," Neomit Dekel-Chen told Israeli news site Ynet.

Ms Dekel-Chen said one woman, her friend Efrat Katz, was shot and killed.

Six months later, an Israeli Air Force investigation acknowledged that it was likely an attack helicopter, which had targeted the wagon, had killed Efrat Katz.

The probe found that the hostages could not be distinguished from terrorists.

Nevertheless, Air Force chief Major General Tomer Bar said he "did not find fault in the operation by the helicopter crew, who operated in compliance with the orders in a complex reality of war".

The military has also confirmed troops were ordered to fire at a home, despite knowing there were civilians being held hostage inside.

In Kibbutz Be'eri, where 101 Israeli civilians died, a tank was ordered to fire upon at least one house, after a prolonged firefight with around 40 Hamas gunmen who had been holding 15 hostages inside and outside.

The "Pessi's house" incident has become notorious in Israel, named after the resident, Pessi Cohen, who was killed along with other hostages being held there.

It was the two survivors who revealed the Israeli military had fired on the house.

"We know that at least one hostage was killed by one of the shells," relative and October 7 survivor Omri Shifroni told the ABC.

Three of Mr Shifroni's relatives were killed in Pessi's house while he was hiding on the other side of the kibbutz with his wife and children.

"There are a few others that we still don't know and we may never know what exactly killed them," he said.

Mr Shifroni's aunt Ayala and her grand-niece Liel and grand-nephew Yanai were all killed at Pessi's house — he believes by terrorists.

But he remains upset about the Israeli military's decision to use heavy munitions on homes in Be'eri.

"I think the real question, the moral question, is whether it's the right thing to do — to fire tank shells on a house with hostages — even though it's selective shooting," he said.

"I think it was not the right decision, not a good decision and not moral.

"But I can also understand there was great chaos in Be'eri and there was a lot of pressure to end the event there.

"I think they didn't intend to shoot and to kill hostages, but when you shoot a tank shell on a house, you need to take into account that that is likely to happen."

Israeli philosopher Asa Kasher told the ABC the directive did not apply to civilian hostages

"That's a new situation, and all the considerations are different," Professor Kasher said.

"Killing the civilian in order to foil the attempted abduction is really [wrong] … everyone understands that that's way outside of what is allowed in a democracy."

Professor Kasher said he was dismayed by reports soldiers had applied the Hannibal Directive on October 7.

"They acted on very low professional standards," he said.

"That's insane, it's not the nature of a democracy, it's not the nature of the IDF, it's not the nature of the command."

Military clears itself of wrongdoing

In response to repeated requests from Be'eri survivors and relatives of those killed there, the IDF has opened an investigation into its actions in the kibbutz.

In July, it released its operational review, but many in Be'eri were not satisfied.

The military cleared Israeli forces of any wrongdoing, finding that a tank only fired "near" the house when negotiations to release the hostages had failed.

"The team determined that, based on the information reviewed and to the best of their understanding, no civilians inside the building were harmed by tank shell fire, except for an isolated incident outside the building where two civilians were harmed by shrapnel," the report stated.

"The team determined that most of the hostages were likely murdered by the terrorists, and further inquiries and reviews of additional findings are necessary."

Sharon Cohen, the daughter-in-law of Pessi Cohen, told Israeli radio she did not accept the investigation's conclusions.

"That's not really true [that hostages were not harmed by tank shells]," she told Israel's Radio Bet on July 14.

"Out of personal privacy issues, I can't really get into the details. These are details that we were told would be investigated again.

"In addition, I'll say that because the incidents in the kibbutz were so exceptional and strange and difficult, the whole issue of removing the bodies, and autopsies, and all those things — essentially were not done."

The IDF review also contradicts testimony from one of the two survivors of Pessi's house, Yasmin Porat, who told Israel's Kan radio on October 15 that the Hamas gunmen had not threatened the hostages and had intended to negotiate with police for their safe return to Gaza.

She said an Israeli police special unit had started the gun battle by firing upon the house, catching "five or six" kibbutz residents outside in "very, very heavy crossfire".

In the interview, she was asked: "So our forces may have shot them?"

"Undoubtedly," she replied.