Human Rights Watch criticised Oman Tuesday for refusing to grant a rights activist bail pending an appeal of his conviction using the Internet to sow unrest in the normally stable sultanate.
Blogger Saeed Jaddad, 48, was jailed this month for three years on charges of undermining the status and prestige of the state, inciting rallies via social media ahead of the anniversary of February 2011 protests and calling for what could undermine public order.
He was also fined 1,000 rials ($2,600/2,385 euros), HRW said.
Jaddad's family paid the fine and posted bail, but "the court refused to release him citing separate charges before another court for his online activities," said Joe Stork, deputy Middle East and Africa director.
"The evidence indicates that Jaddad is in prison simply for criticising the Omani government and its policies," Stork said in the statement.
"Oman should release Jaddad immediately and drop the outstanding charges against him," he added.
Protest broke out in the usually calm sultanate in 2011, taking their cue from Arab Spring uprisings, which prompted Sultan Qaboos to reshuffle his government and usher in reforms.
Amnesty International warned in January that Jaddad's health was seriously deteriorating after he went on hunger strike to protest his detention.
He was hospitalised on January 23, before being returned to custody in his hometown of Salalah.
The prominent activist and blogger, described by Amnesty as a "prisoner of conscience," was arrested in December.
Scores of activists have been convicted of defaming or using social media networks to insult the sultan, who has ruled for 44 years.
Others have either been convicted or are being tried for taking part in demonstrations calling for political reform.
In its annual report last year, US-based independent watchdog Freedom House assigned Oman with an overall 5.5 freedom rating, with one being the best and seven the worst.