"This policy, inflicted as part of a mass killing of Palestinian civilians in Gaza, means Israeli authorities have committed the crime against humanity of extermination, which is ongoing. This policy also amounts to an 'act of genocide' under the Genocide Convention of 1948," Human Rights Watch said in its report.

Israel has repeatedly rejected any accusation of genocide, saying it has respected international law and has a right to defend itself after the cross-border Hamas-led attack from Gaza on Oct. 7, 2023 that precipitated the war.

In a statement on X, Israel's foreign ministry wrote: "The truth is the complete opposite of HRW's lies."

"Since the beginning of the war, Israel has facilitated the continuous flow of water and humanitarian aid into Gaza, despite operating under constant attacks of Hamas terror organization," the statement said.

Although the report described the deprivation of water as an act of genocide, it noted that proving the crime of genocide against Israeli officials would also require establishing their intent. It cited statements by some senior Israeli officials which it said suggested they "wish to destroy Palestinians" which means the deprivation of water "may amount to the crime of genocide".

"What we have found is that the Israeli government is intentionally killing Palestinians in Gaza by denying them the water that they need to survive," Lama Fakih, Human Rights Watch Middle East director told a press conference.

In its response, Israel said it had ensured water infrastructure remained operational. It said international partners had sent water tankers through Israeli crossings, including last week, and ⁠Israel had facilitated the entry of more than 1.2 million tons of humanitarian supplies into Gaza.

Human Rights Watch is the second major rights group in a month to use the word genocide to describe the actions of Israel in Gaza, after Amnesty International issued a report that concluded Israel was committing genocide.

Both reports came just weeks after the International Criminal Court issued arrest warrants for Israeli Prime Minister Benjamin Netanyahu and his former defence chief for alleged war crimes and crimes against humanity. They deny the allegations.

The 1948 Genocide Convention, enacted in the wake of the mass murder of Jews in the Nazi Holocaust, defines the crime of genocide as "acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group".

The 184-page Human Rights Watch report said the Israeli government stopped water being piped into Gaza and cut off electricity and restricted fuel which meant Gaza's own water and sanitation facilities could not be used.

As a result, Palestinians in Gaza had access to only a few litres of water a day in many areas, far below the 15-liter-threshold for survival, the group said.

Israel launched its air and ground war in Gaza after Hamas-led fighters attacked Israeli communities across the border 14 months ago, killing 1,200 people and taking over 250 hostages back to Gaza, according to Israeli tallies.

Israel's campaign has killed more than 45,000 Palestinians, displaced most of the 2.3 million population and reduced much of the coastal enclave to ruins.