Amnesty International has lambasted Bahrain's decision to uphold the conviction of opposition leader Sheikh Ali Salman and increase his prison sentence from four to nine years.
The London-based rights group said the decision by Bahrain authorities on Sunday is "a shocking attack on the right to freedom of expression."
"Sheikh Ali Salman’s conviction is clearly politically motivated and is designed to send a message to others that even legitimate and peaceful demands for reform will not go unpunished," said James Lynch, deputy director of the Middle East and North Africa Programme at Amnesty International.
Sheikh Salman is "a prisoner of conscience and should never have been put on trial in the first place. He must be immediately and unconditionally released,” said Lynch.
The Shia cleric, who is the secretary general of the main opposition party al-Wefaq, was originally sentenced on June 16, 2015 to four years in prison after a trial which Amnesty described as "unfair."
The Bahrain tribunal charged him with “publicly insulting the Interior Ministry” and “publicly inciting others to disobey the law” in his speeches.
His appeal had been pending for eight months but the Court of Appeal finally rejected it in the capital Manama on Sunday and raised Salman's jail term to nine years.
In recent years, Bahrain has tightened its grip on freedom of expression with multiple arrests and harassment of opposition politicians and activists.
Amnesty also mentioned Ebrahim Sharif, former secretary general of the National Democratic Action Society (Wa’ad) who was imprisoned for one year on February 24 for calling for reform in a speech.
Another prisoner, former secretary of the Wahdawi party Fadhel Abbas Mahdi Mohamed, serves a five-year sentence after an "unfair" trial in June 2015 for condemning Saudi airstrikes in Yemen.
“With three prominent opposition politicians behind bars, the authorities have made clear that criticism will not be tolerated in Bahrain today and anyone who dares to challenge them is at risk,” Lynch said.
Amnesty said it considers the three men "to be prisoners of conscience imprisoned solely for peacefully expressing their views."
On Tuesday, hundreds of Bahrainis held protests throughout the capital Manama, venting rage at the ruling against Sheikh Salman.
Bahrain, a close ally of the US in the Persian Gulf region, has been witnessing almost daily protests against the ruling Al Khalifa dynasty since mid-February 2011.
The tiny sheikhdom's heavy-handed crackdown on demonstrations with the help of Saudi Arabia has left scores of people dead and hundreds injured.