Thirty Emiratis and Egyptians went on trial on Tuesday accused of setting up an illegal branch of Egypt's Muslim Brotherhood in the United Arab Emirates.
The Federal Supreme Court in Abu Dhabi adjourned the case, which is viewed as an attempt to stamp out what the UAE says is a threat from political Islam, until Nov. 12.
The UAE, a U.S. ally and major oil exporter, has long been distrustful of the Muslim Brotherhood, which helped propel Egypt's Mohamed Mursi to power last year. The UAE has welcomed Mursi's ouster by the army after mass protests against his rule.
Twenty Egyptians, six of whom are being tried in absentia, and 10 Emiratis are charged with setting up an illegal branch of the Muslim Brotherhood in the UAE, stealing and airing state security secrets and collecting funds illegally, activists said.
The defendants denied all the charges, a family member of one of the detainees who attended the trial told Reuters, adding that some of the Egyptians had said they were physically abused in custody and their confessions were obtained under coercion.
"One Egyptian said they were subjected to all kinds of torture," the family member said, on condition of anonymity.
The UAE denies using torture. The court ordered medical tests for some of the defendants, state news agency WAM said.
The 10 Emiratis who went on trial on Tuesday are among 61 Islamists convicted by a UAE court in July of plotting to overthrow the government, activists said.
Many of the jailed Islamists are members of the al-Islah group, which the UAE says has links to Egypt's Brotherhood. Al-Islah denies any organisational links to the group.
New York-based Human Rights Watch (HRW) has raised concerns about Tuesday's trial and questioned the ability of the UAE judicial system to uphold basic rights of free speech and peaceful association.
Thanks to its state-sponsored cradle-to-grave welfare system, the UAE has largely avoided the unrest that has unseated long-serving Arab rulers elsewhere in the region.
But it has shown little tolerance towards dissent. Dozens of people have been detained since 2011 and most were tried and convicted of planning to overthrow the government.
Egypt's Muslim Brotherhood said at the time of their arrests that some of the Egyptians now on trial are its members and said they had been wrongfully arrested.
Relations between Cairo and Abu Dhabi soured after Hosni Mubarak was toppled as Egypt's president in 2011. He had been a longtime ally of the Gulf Arab states.
The rise of the Brotherhood in Egypt since 2011 unsettled most Gulf Arab states, including the UAE, which feared it would embolden Islamists at home.
Days after the army ousted Mursi in July, the UAE offered $3 billion in support for Egypt's economy.
Mursi himself is facing trial in Cairo along with 14 other Islamists on charges of inciting violence. He appeared in court on Monday for the first time since he was deposed on July 3.