Bahrain's appeals court acquitted nine medics and cut the jail terms of nine others on Thursday for their role in anti-regime protests last year, in a case widely criticised by 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 encampment at 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 for appeal."
The 18 who had been arrested have been free on bail since September and did not appear in court.
Defence lawyers told AFP earlier on Thursday that those who were handed a sentence of "one year in prison or less" have already served their terms and are not expected to be re-arrested.
But judicial sources later said that only the five handed a sentence of "less than one year" will not be jailed again.
To be implemented, the "sentence is awaiting an arrest warrant from the prosecution for four defendants," the same sources said.
Among the four are consultant orthopaedic surgeon Ali Alekri, whose initial 15-year jail term was cut to five years, and Ibrahim al-Damstani, the Bahraini Nursing Society secretary general, sentenced to three years.
They will both have time left to serve.
The other two are doctors Ghassan Daif and Saeed al-Samaheji -- both of whom were sentenced to one year in prison.
Rula al-Saffar, who heads the society and had faced 15 years in jail, was among those acquitted, judicial sources said.
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"At first they were 13 charges against me. They were all later dropped except for plotting to overthrow the regime and gathering illegally," he told AFP by telephone.
"We hope to reach the Court of Cassation while out of jail," he said referring to Bahrain's top court which will now handle the case.
But according to the government statement, "no medic is being charged for treating protesters."
"The charges brought against the medics were primarily for their involvement in politicising their profession, breaching medical ethics and, most serious of which, was their call and involvement in the overthrow of the monarchy," it said.
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.
They were handed sentences of between five and 15 years by a semi-military tribunal last September but retried in civil court after the public prosecutor dismissed confessions allegedly extracted under torture.
The doctors had also stood accused of spreading false news -- particularly concerning the condition of wounded protesters -- illegal acquisition of medicines and medical facilities and of participating in demonstrations.
Reacting to the news, London-based rights group Amnesty International urged the authorities to quash the convictions, saying "no evidence was presented to prove they committed any crime and (it) believes the accusations against them are unfounded.
"This is a dark day for justice in Bahrain," said Hassiba Hadj Sahraoui, Amnesty's deputy director for the Middle East and North Africa.
"These are politically motivated charges against medical professionals who were working to save lives amid very trying circumstances."
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.