The 57-page report by Human Rights Watch details widespread abuse and humiliation of suspects being held without trial under national security laws in Malaysia.
The country is a close US ally in the "war on terrorism" and has shared intelligence with Washington about alleged al-Qaida-linked operations in southeast Asia and the 11 September attacks.
The New York-based group's report, to be released on Tuesday, compares the abuse to US troops' mistreatment of Iraqi prisoners and alleged violations in Afghanistan and Guantanamo. It says US abuses carried out in the name of the alleged war against terrorism have given other nations an excuse to do likewise.
"US abuse of detainees in Iraq, Afghanistan and Guantanamo shows what can happen behind closed doors," Sam Zarifi, Human Rights Watch's deputy director for Asia, said in a statement.
"The Malaysian government uses Guantanamo as a sword and a shield," he said. "Abuses by US authorities in the 'war on terror' give cover to governments that abuse their own citizens."
Malaysia's government has rejected the abuse allegations, which were reported last week by The Associated Press after obtaining detainee statements, smuggled out of the prison camp where they are held and other documents, compiled by lawyers and local rights groups.
Foreign Minister Said Hamid Albar said the report did not prove authorities had acted excessively and accused the rights group of unfairly singling out Malaysia.
"I think these are wild allegations," Hamid said. "I do not know what is their intention, but there are so many abuses of human rights elsewhere that they need to pay particular attention to. Don't keep harping on countries that have got a very good and clear track record."
"The Malaysian government uses Guantanamo as a sword and a shield ... Abuses by US authorities in the 'war on terror' give cover to governments that abuse their own citizens"
Asia's Human Rights Watch
Since early 2001, more than 100 suspects have been arrested in Malaysia under the Internal Security Act, most of them alleged members of Jamaah Islamiyah, an al-Qaida-linked group blamed for a string of bombings that have killed hundreds of people in Southeast Asia in the past four years.
The Act allows for a 60-day interrogation period by Malaysia's Special Branch, which then makes recommendations to Prime Minister Abd Allah Ahmad Badawi, in his capacity as home minister, about whether to imprison a suspect under a two-year order, renewable indefinitely.
Detainees say most of the alleged abuses occurred during the interrogation period. They claim they were routinely kicked, slapped, forced to strip and stand in uncomfortable positions for long periods, verbally abused and humiliated while being peppered with questions in sessions lasting up to 24 hours.
According to the report detainees were threatened with beatings from wooden sticks and rubber hoses and told members of their families would be arrested.
Malaysian Foreign Minister Said
Albar (R) criticised HRW report
Special Branch interrogators told some detainees they would face years in prison if they did not cooperate, or would be sent to Guantanamo Bay, the report said.
"They told me, if you are sent to Cuba, the torture is severe," the report quoted one former detainee as telling a Human Rights Watch interviewer. "You might lose an arm or a leg, you might be paralysed."
Human Rights Watch said the extent of the alleged abuse was unknown because access to detainees was extremely limited, and had urged Malaysia to launch an independent investigation.
The report criticises Washington for not challenging the detentions as "testament to the significant erosions in respect for international human rights norms" since the September 11 attacks.
"They told me, if you are sent to Cuba, the torture is severe ... You might lose an arm or a leg, you might be paralysed"
Human Rights Watch said the Malaysian government had shown its willingness to support US violations of international law and the rights of its own citizens in counterterrorism cases, citing the treatment of 13 Malaysian students arrested last year at an Islamic school in Pakistan.
Malaysian officials were silent and did not respond to relatives' requests for information about the 13 as they were held for about seven weeks in Pakistan, where they were interrogated by US and other officials, the report says.
The report alleges the group were coerced into making incriminating statements with threats of violence and being sent to Guantanamo, before being returned to Malaysia, where they were arrested under security laws.