In a report published Wednesday, Human Rights Watch found that Hamas and other militant groups committed multiple war crimes during the Oct. 7 attack on southern Israel. 

The New York-based organization said the Al-Qassam Brigades, Hamas's military wing, and at least four other Palestinian armed groups committed "crimes against humanity" against civilians during the deadly attack.

In the 236-page report, HRW found that Hamas and the four groups violated international law by killing and torturing people, taking hostages, looting and committing crimes involving sexual and gender-based violence during their attack on Israel.

"This report details numerous incidents of violations of international humanitarian law — the laws of war — by Palestinian armed groups on October 7, 2023; it does not include violations since then," it says.

HRW demanded Hamas immediately release the remaining hostages and bodies of hostages still being held in Gaza. It called on all sides to adhere to international law and agree to a ceasefire as soon as possible.

HRW calls for an investigation

The organization's research for the report included interviews with 144 people, including survivors of the Oct. 7 attack, journalists and medical experts, and verifying over 280 photos and videos, such as those from fighters' body cameras. It also looked at satellite images and audio recordings shared on the armed groups' Telegram channels.

It said its researchers could not independently verify claims of rape and sexual violence, using sources including media and United Nations reports.

HRW called for an investigation into other alleged crimes against humanity by Hamas fighters, including sexual violence and persecution against an identifiable group on racial, national, ethnic or religious grounds.

WATCH | A March UN report found 'reasonable grounds' of sexual violence on Oct. 7: 

UN finds ‘reasonable grounds’ of sexual violence during Oct. 7 attacks

WARNING: Video contains graphic images | A UN team deployed to Israel says it found ‘reasonable grounds’ to back up allegations that Hamas committed sexual violence during the Oct. 7 attacks, and that such violence is likely ongoing.

Hamas led the Oct. 7 attack on southern Israel that killed some 1,200 civilians and military personnel and took about 250 hostages into Gaza, according to Israeli figures. Israel's subsequent incursion on Gaza has killed more than 38,000, by the Palestinian count, over the last nine months of the war.

The militants committed a crime against humanity when they launched a "widespread attack directed against a civilian population," said Belkis Wille, an HRW associate director who arrived in Israel days after the October attack and spent months researching it with local staff. 

"The killing of civilians and taking of hostages were all central aims of the planned attack," Wille said, "and not actions that occurred as an afterthought or as a plan gone awry, or as isolated acts, for example, perpetrated by unaffiliated Palestinians from Gaza."

Hamas demands withdrawal of report

In a post on Telegram, Hamas rejected the report's findings and demanded the "withdrawal of the report," and an "apology from HRW." It said HRW "moved away" from a scientific, research-based methodology and didn't adopt a neutral position. The post also says the report echoes what it called lies told by Israel. It called the report an "Israeli propaganda document." 

In Gaza, Muhammad Hamdan, who lives in Khan Younis, told CBC freelance videographer Mohamed El Saife that he doesn't agree with the report's findings. 

"Israel is the one who committed crimes against the Palestinian people," he said. "So we demand all the concerned authorities to stand seriously with the Palestinian people, and specifically in the Gaza Strip."

Hamdan said he has lost 18 family members in Israeli airstrikes on his neighbourhood, and that the blame rests on Israel. 

"Israel humiliated us," he said. "It destroyed our homes on top of us."

WATCH | More on Muhammad Hamdan, the sole survivor of his family: 

Displaced Gaza man loses 18 family members

Muhammad Hamdan, who lives in Khan Younis, is the sole survivor of his family after losing 18 family members. They were civilians with no affiliation with Hamas, he says.

Hamdan walked the site of his home, completely destroyed from the fighting. He climbed over rubble and walked streets he no longer recognized. 

"If it was in any other country, they wouldn't see destruction like this."

Previous HRW reports on alleged Israeli war crimes

HRW has also previously released reports on alleged war crimes by Israel during the country's ongoing invasion of the Gaza Strip, including an Oct. 31 airstrike on a residential building that killed at least 106 civilians.

Its latest report noted what it called Israel's "undetermined number of unlawfully indiscriminate attacks," as well as the ordered evacuation of everyone in northern Gaza on Oct. 13 that HRW said risked forced displacement, a war crime.

WATCH | ICC issues arrest warrants for leaders of Israel, Hamas: 

Arrest warrants sought for leaders of Israel, Hamas

Warning: Video contains disturbing details | The chief prosecutor of the International Criminal Court announced he is seeking arrest warrants for the leaders of Hamas and Israel's prime minister, on suspicion of war crimes and crimes against humanity. The move is being internationally condemned as a false equivalence and a moral outrage.

In the aftermath of Oct. 7, HRW said, Israel cut off essential services in Gaza, including water and electricity. It also blocked "all but a trickle of fuel and humanitarian aid" — all acts that amount to war crimes, it said.

Israel has denied allegations of war crimes.

HRW's report comes as both Israeli and Hamas leaders face arrest warrants from the International Criminal Court in connection with their actions during the war in Gaza, which is stretching into its 10th month.