Jerusalem(CNN) Palestinian authorities in the West Bank and Gaza have engaged in a systematic crackdown on dissent, including the use of torture that may amount to a crime against humanity, according to a new report from Human Rights Watch.

"Relying primarily on overly broad laws that criminalize activity such as causing 'sectarian strife' or insulting 'higher authorities,' the [Palestinian Authority] and Hamas use detention to punish critics and deter them and others from further activism," wrote Human Rights Watch, or HRW, in the report.

"We documented dozens of cases of people detained for a Facebook post, for writing a critical article in a mainstream publication, for protesting, for being involved with the wrong group or movement," said Omar Shakir, Israel-Palestine director for HRW, at a press conference in Ramallah announcing the report. In detention, detainees routinely are threatened, beaten, subjected to foot whipping, in many cases subjected to torture."

The report, titled "Two Authorities, One Way, Zero Dissent," was compiled over two years, drawing on 86 cases and 147 interviews, many with ex-detainees, according to HRW. The two authorities -- the Palestinian Authority in the West Bank and Hamas in Gaza -- have cracked down on political opposition, social media criticism, journalists, demonstrations, and opposition on university campuses, HRW said, adding that the authorities' alleged practices in detention "may amount to a crime against humanity, given its systematic practice over many years."

The consequence of the crackdown in both places is a chilling effect on "free speech, association, and assembly," HRW said.

In one case detailed in the report, 55-year-old Abdullah Abu Sharkeh from the Jabalia Refugee Camp in Gaza was detained four times in one year for criticizing Hamas on social media. On May 29, 2017, he was arrested for saying on Facebook that Hamas ruled by "iron and fire." Abu Sharkeh was made to stand or sit for hours at a time in a small chair, leaving him with severe pain in his back, neck and knee for days after his detention. Abu Sharkeh was released after five days when he he signed a confession that said he would not "slander persons in high national positions."

It is rare for a human rights organization to direct its criticism at both Palestinian authorities at the same time -- the two are separated by a bitter, decadelong feud, which can make it difficult to investigate both authorities together.

The Palestinian Authority and Hamas are widely seen as the chief rivals for support among Palestinians. And while the Palestinian Authority enjoys widespread international legitimacy, as witnessed by the list of states that support it, Hamas is regarded by the United States and the European Union, among others, as a terrorist organization.

Both authorities, notes HRW, have mechanisms in place for receiving citizen complaints to allow for the investigation of accusations of wrongdoing by security forces, but in practice, these mechanisms rarely lead to impartial investigations or disciplinary actions.

The two authorities rely on international support. The security forces of the Palestinian Authority rely primarily on assistance from the United States, as well as assistance from a number of European states. Hamas relies on the financial support of Iran, Qatar and Turkey. HRW recommended these countries suspend assistance to the security forces until the authorities take steps to end "arbitrary arrests and torture."

In addition, HRW recommended that authorities in the West Bank and Gaza publicly pledge to end arbitrary arrests and torture, investigate allegations of abuse, and take further measures to ensure fair and impartial treatment of detainees. HRW also advised social media companies and internet service providers to carefully scrutinize every government request for user data.

CNN reached out to the Palestinian Authority for comment but has not received a response.

A response from the Palestinian Authority's Police General Directorate, included in the HRW report, denies any allegations of arbitrary arrests or torture. "Guidance issued by the Ministry of the Interior ... mandate the application of the law and guarantee the proper legal procedures and the preservation of freedoms and rights and prevent their violation or restriction except within the bounds of the law," the response says.

Eyad Al Bozom, a spokesman for the Hamas-run Interior Ministry in Gaza, told CNN the report "involves lots of exaggeration and inaccurate information."

"We do not allow torture, we do not silence mouths and we abide by Palestinian law. We recognize the freedom zone in Gaza as a large area," Al Bozom said.

European diplomats approached by CNN said they were looking at the report, however none had any immediate comment. CNN also reached out to the United States for comment but has not received a response.