Human Rights Watch on Wednesday called for the immediate release of a man holding dual US and Saudi citizenship and detained by Saudi authorities for writing comments on Twitter about the Koran.
HRW said Mohammad Salama has been held since April without charge after he was arrested for posting tweets criticising interpretations of the sayings of the Muslim Prophet Mohammed, also known as the hadiths, on his Twitter account.
It said that in March Salama wrote that the "the Prophet himself questioned the Koran" and that "thoughts of suicide are normal, because the Prophet himself contemplated it."
He also posted a video on YouTube criticising a cleric for his political views after which unidentified online commentators called for his arrest and execution.
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HRW said that neither Salama or his family have been informed of accusations against him.
"Salama's case is a sad example of the way that Saudi authorities hold detainees for extended periods of time without charge and in violation of major human rights standards," Joe Stork, HRW's deputy Middle East director, said in a statement.
"Authorities have shown no evidence that he did anything more than express his opinion peacefully. He should be released immediately."
HRW said another Saudi, Hamza Kashgari, has also been in custody since February 12 for his tweets discussing religion.
Saudi authorities arrested and detained Kashgari immediately after Malaysia extradited him, despite pleas by human rights organisations not to send him back to Saudi Arabia.
Kashgari had posted messages on his Twitter account that top Saudi clerics said committed apostasy, HRW said.