A Bahraini doctor, sentenced to jail for his role in last year's anti-regime protests and currently on bail, went on hunger strike Thursday to protest the verdict, the main Shiite opposition group said.

Saeed al-Samaheji, who faces a year in prison, began the strike at one of Al-Wefaq's offices in the Zinj neighbourhood of the capital, the opposition group said, adding that the doctor had descrbed the sentence as "political."

Last week, Bahrain's appeals court acquitted nine medics and cut the jail terms of nine others for their role in anti-regime protests last year, in a case widely criticised by human rights groups.

Two others arrested in the crackdown, who remain at large, did not appeal.

The 20 doctors and nurses worked at Manama's Salmaniya Medical complex, stormed by security forces after a crackdown on a protest camp in the capital's nearby Pearl Square in March 2011.

The government said nine of the defendants "were found innocent, five will be released for time served, while four that were convicted still have their right of appeal."

The 18 who had been arrested have been out on bail since September and did not appear in court.

The medics had faced a plethora of charges, the most serious of which was occupying the vital medical centre and possessing weapons while denying Sunni Muslims access to the hospital as Shiite demonstrators camped in the car park.

Claims of torture against scores of Shiite detainees were upheld in November by the Bahrain Independent Commission of Inquiry, a panel tasked by King Hamad with probing the crackdown after an international outcry over alleged abuses.

King Hamad said he was "dismayed" by the findings of the report concerning the use of torture and pledged reforms.

The medics had insisted they were innocent. The commission's report stated charges that they inflated the number of protesters injured were unfounded, noting hospital records showed hundreds were admitted in mid-February.

Many of the 20 medics -- 15 of whom are doctors -- alleged they were tortured in prison.