Activist Ali Saqer died in prison last month, had been charged with attempting to run over a policeman
Bahrain has said it will try five prison guards over the death in police custody of a Shi'ite activist during protests by the Gulf kingdom's Shi'ite majority.
The guards' arrests and trial were reported by the Bahraini news agency BNA late on Wednesday as Bahrain prepared to lift martial law imposed during weeks of pro-democracy protests led mainly by Shi'ites calling for greater political freedoms, a constitutional monarchy and an end to sectarian discrimination.
At least 29 people, all but six of them Shi'ites, have been killed since the protests started in February, inspired by Arab revolts against autocratic rule that toppled the rulers of Egypt and Tunisia.
Four policemen also died during the unrest, including at least two run over by the cars of Shi'ite protesters. The six non-Shi'ites killed included the four policemen.
Activist Ali Saqer, who died in prison last month, had been charged with attempting to run over a policeman with his car in March.
"The investigations carried out so far have shown that there is evidence that five guards of the detention cell of the deceased violated the law and committed criminal acts," BNA reported the Interior Ministry's Undersecretary for Legal Affairs as saying in a report on Wednesday.
"They were arrested and will be tried by the concerned military court."
The island kingdom has been preparing to end its state of emergency on June 1, but the opposition says hundreds of people have been arrested and four died in police custody in April.
Human Rights Watch said on Wednesday that Bahrain should suspend prosecution of civilians in military courts and set up an impartial body to look into allegations of torture during a clampdown on those involved in the protests.
A trial of a group of opposition activists charged with attempting to topple the government will resume on Thursday.
Separately, Saudi-led forces will stay in Bahrain after the state of emergency is lifted "in anticipation of any foreign threat", the head of Bahrain's military was reported as saying by BNA on Wednesday.
Commander-in-Chief Marshal Sheikh Khalifa bin Ahmed al-Khalifa said tough measures would be taken if protesters returned to the streets.
"I say to those who did not get the message, if you return we will come back stronger this time."