Representatives of Gaza's Islamist Hamas government turned up at a Human Rights Watch press conference in Gaza on Wednesday to dispute a recent report compiled by the international rights group accusing Hamas of torture and other abuses of justice.

The surprise appearance by Hamas government representatives turned the news conference into an open debate, an uncommon display in the Gaza Strip where, in the past, Hamas would probably have remained aloof or prevented such a press event on its turf.

The rights group said Wednesday that Hamas security forces in the Gaza Strip had committed rampant abuses against Palestinian prisoners, including beatings with metal clubs and rubber hoses, mock executions and arbitrary arrests, and urged the Islamic terror group to swiftly reform its criminal justice system.

The Human Rights Watch report  was researched in Gaza with the knowledge of the Palestinian Islamist movement.

The rights group cited the case of Abdel Karim Shrair, who was arrested by Hamas in August 2008 and tortured for three weeks, according to the man's family and lawyers.

Shrair faced further abuse at the hands of Gaza's internal security agency and was denied visits for weeks, the report said. He was then charged with collaborating with Israel based on confessions made under torture, according to his lawyer.

Shrair's mother, Safia Ahmad Shrair, told HRW that when she was allowed to see him in October of that year, his legs and face were bruised, his feet were swollen, his hands and arms had rope marks, and his chest had burn marks.

Hamas executed Shrair in 2011 by firing squad. His mother said Hamas forbade the family from burying him themselves and beat her with sticks when she tried to hold his body.

In its report, HRW alleged that such practices were not limited to suspected political offenses.

It cited one man, identified only as a lawyer named "Y'' for fear of reprisals, who said he was arrested for fraud by Hamas police who ransacked his office and confiscated his passport, client files and other items.

"Y," who denied the allegations, described being tied to a bed and beaten with a rubber hose and metal clubs and forced to drink bleach that along with other forms of torture made him lose consciousness, according to the report.

He told HRW he woke up in a Gaza hospital where interrogators continued to beat him and then bound his hands behind his back and tied them to a window until his body was partly suspended off the ground for several hours.

The report said that many Palestinians who were tortured were too scared to complain, fearing retribution by Hamas. It also said hospital officials often refuse to release medical records of torture victims to avoid them being used as evidence.

The report also accused Hamas police of making random arrests without warrants and sometimes holding family members as a pressure tactic. People are often detained without charge and denied access to lawyers and family, according to HRW.

Hamas insisted the report was "politically motivated." Hamas has run Gaza unopposed since it seized control in 2007, suppressing rivals in the Fatah movement and launching sporadic attacks against Israel, which maintains a partial blockade of the coastal strip to prevent the entry of arms.

Bill Van Esveld, an HRW Middle East researcher who chaired the press conference, said the presence of Hamas media officials was surprising. "They knew it was happening but they were not invited," Esveld told Reuters.

Hamas refuses to accept the legitimacy of the state of Israel and is ostracized in the West as a terrorist group. But its ties with Iran have frayed since the Arab Spring of popular uprisings and it is now allied to Egypt's elected Muslim Brotherhood rulers and working to improve its image.

Hamas cooperated with HRW's Joe Stork, deputy Middle East director of the New York-based rights group, who visited the enclave to conduct interviews and research. Hamas officials did not reply to his written questions, but Stork did meet the minister of justice and the director of internal security.

They were not quoted in the 43-page report, Hamas said.

Islam Shahwan, spokesman for the Hamas interior ministry, confronted Esveld and accused the rights group itself of misrepresenting the reality of the situation in Gaza. "Your report has many mistakes in it," Shahwan told Esveld in front of television cameras.

Human Rights Watch, which is based in New York, urged Hamas to "stop the kind of abuses that Egyptians, Syrians and others in the region have risked their lives to bring to an end" — an allusion to Arab Spring uprisings.

"After five years of Hamas rule in Gaza, its criminal justice system reeks of injustice, routinely violates detainees' rights and grants impunity to abusive security services," Stork said in a statement.

According to Human Rights Watch, witnesses reported that Hamas's Internal Security agency, the narcotics unit of the civil police force and police detectives have all tortured detainees.

"The Hamas authorities have failed to investigate and prosecute abusive security officials, and have in practice granted immunity from prosecution to officials in the Internal Security service in particular," Human Rights Watch reported.

Shahwan said the report was "politically motivated and relied, in part, on guesses rather than facts."

He mentioned, however, that Hamas authorities had dismissed or detained 120 security personnel for what he termed "violations" since 2007.

Calling for a moratorium on the death penalty, the report said Hamas had executed three men in the past five years on the basis of confessions extracted under torture.

"Some of the Gaza abuse victims were people detained on suspicion of collaborating with Israel or the Palestinian Authority in the West Bank," it said. "Collaboration is a serious crime under Palestinian law, but suspicion of collaboration does not justify torture or other abuse."