DUBAI: Human Rights Watch called on Bahrain's king on Monday to overturn convictions against nine medics for their role in last year's pro-democracy uprising, saying confessions had been obtained by torture and trial proceedings were unfair.

Bahrain, a U.S. ally, has been criticised abroad for the verdicts against the doctors and nurses who treated those injured in the uprising which began in February last year and helped bring world attention to their plight before the revolt was crushed a month later.

In the absence of a political solution, the Gulf Arab kingdom has remained in turmoil with smaller scale protests by the Shi'ite Muslim majority against the Sunni rulers and clashes almost daily.

Bahrain's Court of Cassation last week rejected all appeals presented by the medics, all of them Shi'ites, and upheld the previous rulings of prison terms ranging between one month and five years.

Bahrain, home to the U.S. Navy's Fifth Fleet, accuses regional Shi'ite power Iran of encouraging the unrest and has promised a tough response to violent protests as talks with the opposition have stalled.

The U.S.-based rights group urged Bahrain's King Hamad to order the release of the medics who were re-arrested on Tuesday, and said "convictions were based in part on confessions obtained by torture and in proceedings that were fundamentally unfair".

"We are reluctant to call on the king to reverse a judicial decision, but time and again we have seen Bahraini courts uphold politically motivated charges against those who peacefully dissent," said Joe Stork, deputy Middle East director at Human Rights Watch in a statement.

"The courts have failed to uphold Bahrain's obligation to protect free expression and peaceful assembly."

The medics were freed from detention last year after an outcry over allegations of torture. The charges against them included inciting hatred and calling for the overthrow of Bahrain's rulers.

The doctors and nurses say they were victimised for treating protesters and helping bring world attention to deaths at the hands of security forces.

Washington said it was deeply concerned after last week's ruling and Amnesty International said it considered the jailed medics prisoners of conscience.

The Sunni Al Khalifa family used martial law and the help of Saudi-led Gulf troops to put down last year's uprising. Thousands were arrested and military trials were instituted during the martial law period.

Widespread and excessive force during the crackdown, including confessions under torture, was detailed in a commission of international legal experts which published its findings in November and recommended measures to stop them.

Bahrain says it has taken steps to address the brutality of security forces by dismissing those responsible and introducing cameras at police stations to monitor abuses.

But little progress has been made in addressing the grievances that led to the uprising.