Amnesty International on Saturday urged Jordan to free six political activists charged with insulting King Abdullah II, saying that at least three of them were beaten during interrogation.
The human rights watchdog "is calling for the immediate and unconditional release of six pro-reform activists held for 'insulting' the king," it said in a statement.
"Amnesty International believes them to be prisoners of conscience held solely for exercising their right to freedom of expression and that they are being punished for their pro-reform views and peaceful activities."
The six men were arrested and charged by military prosecutors in mid-March after a demonstration in the southern city of Tafileh.
Opposition Islamists have demanded the authorities free the activists, and demonstrations have been held in Tafileh and Amman to protest their detention.
If convicted, the six suspects face three years in prison each.
"According to information received by Amnesty International, at least three of them were beaten by security forces during initial interrogations," the London-based organisation said.
"Restrictions on the right to criticise the authorities or state institutions persist in Jordan and journalists, activists and others continue to face arrest and prosecution," it added.
The military State Security Court this month released an 18-year-old political activist from jail after the king pardoned him for burning a picture of the monarch.
Jordanians have been protesting since January last year demanding sweeping political and economic reforms and an end to corruption.