The plaintiffs, relatives of four Israeli-US dual nationals and one visiting US citizen who died in attacks in Tel Aviv, Jerusalem or the occupied West Bank between 2014 and 2016, accused Facebook of helping Hamas militants operate.
The lawsuit, filed in US District Court for the Southern District of New York, argued that Facebook "knowingly provided material support and resources to Hamas ... facilitat(ing) this terrorist group's ability to communicate, recruit members, plan and carry out attacks, and strike fear in its enemies".
The social media giant did not respond directly to the lawsuit but said it stood by its regulations for preventing abusive content and a company representative in Israel said the company wanted "people to feel safe" when using Facebook.
"There is no place for content encouraging violence, direct threats, terrorism or hate speech on Facebook. We have a set of Community Standards ... and we urge people to use our reporting tools if they find content that they believe violates our standards so we can investigate and take swift action."
The private lawsuit follows censure from Israel's security minister over what he deemed Facebook's reluctance to help track potential Palestinian militants and curb incitement to violence. In response, Facebook defended its regulations against online abuse.
Hamas formally claimed responsibility for one of the attacks cited in the lawsuit. The plaintiffs' Israeli lawyer, Nitsana Darshan-Leitner, said they had expert assessments linking Hamas to the other attacks.
Hamas is designated a terrorist organisation by the United States. The lawsuit was brought under the 1992 Anti-Terrorism Act that prohibits American businesses from providing any material support, including services, to designated terrorist groups and their leaders.
Sami Abu Zuhri, a Hamas spokesman in Gaza, called the lawsuit an Israeli attempt to blackmail Facebook and accused Israel of trying to turn the social network into a spy tool against Palestinians.
He said some Israeli politicians and soldiers had "expressed pride at the killing of Palestinians" on Facebook and other social media. "The real test for the owners of Facebook is to reject this (Israeli) pressure," Abu Zuhri said.
Darshan-Leitner, of the Shurat HaDin-Israel Law Centre, filed a class action suit in October for an injunction against Facebook to stop carrying alleged Palestinian incitement. She said proceedings were still under way in that case.For details of the latest launches and news from Samsung, Xiaomi, Realme, OnePlus, Oppo and other companies at the Mobile World Congress in Barcelona, visit our MWC 2025 hub.