"Meta's policies and practises have been silencing voices in support of Palestine and Palestinian human rights on Instagram and Facebook in a wave of heightened censorship of social media," the New York-based group said in a report released Thursday.
"Meta's censorship of content in support of Palestine adds insult to injury at a time of unspeakable atrocities and repression already stifling Palestinians' expression," said Deborah Brown, acting associate director of HRW's technology and human rights division.
On Tuesday, Meta's independent oversight board had already criticised the social media titan for removing posts that showed human suffering in the conflict.
The war began when Hamas attacked Israel on October 7, killing around 1,140 people, mostly civilians, and abducting about 250, according to an AFP tally based on Israeli figures.
Israel's ensuing military campaign in Gaza has so far killed at least 20,000 people, the majority of them children and women, according to the Hamas government.
HRW pointed to "systemic online censorship", reporting more than 1,050 "takedowns and other suppression of content" on Instagram and Facebook from over 60 countries during October and November.
The content in question was posted by "Palestinians and their supporters, including about human rights abuses".
"While this appears to be the biggest wave of suppression of content about Palestine to date, Meta, the parent company of Facebook and Instagram, has a well-documented record of overbroad crackdowns on content related to Palestine," the report added.
Hundreds of people continued to report censorship after the organisation completed its analysis, "meaning that the total number of cases Human Rights Watch received greatly exceeded 1,050," it added.
Of the 1,050 cases reviewed, 1,049 involved "peaceful content in support of Palestine that was censored or otherwise unduly suppressed, while one case involved removal of content in support of Israel," HRW said.
HRW said censorship on Instagram and Facebook included the removal of posts, stories and comments, suspending or disabling accounts, restricting certain features including users' ability to engage with posts or follow certain accounts, as well as limiting the visibility of users' content.
The group said its own posts suffered from restrictions, with dozens of users reporting they were unable to repost, like or comment on a HRW post "calling for evidence of online censorship, which was flagged as 'spam'," it added.
"Meta should permit protected expression, including about human rights abuses and political movements, on its platforms," HRW said.
