Manama: The mass trial of 28 Bahraini health professionals who treated injured anti-government protesters campaigning for greater freedoms in the Gulf kingdom resumed on Monday in a special security court.

The prosecution of 28 doctors and nurses, who were charged with participating in efforts to topple Bahrain's monarchy, signals that the kingdom's Sunni rulers do not intend to end their relentless pursuit of the Shiite-led opposition despite appeals for dialogue.

The outreach by King Hamad Bin Isa Al Khalifa has met a cool reception from Shiite leaders who demand that authorities roll back security measures and halt the trials against activists.

Reports of abuse of Bahrain's leading human rights activist, who's been in custody since April, have further eroded the opposition's appetite for reconciliation talks, set to begin Friday.

The activist, Abdulhadi Al Khawaja, was convicted last week by a special security tribunal of supporting anti-government protesters and sentenced to life in prison along with seven opposition leaders.

Nabeel Rajab, an activist, said that Al Khawajah was severely beaten in prison after the court session and was taken to a military hospital for treatment.

Authorities denied Al Khawajah has been hospitalised and said in a statement to The Associated Press late on Monday that the activist remains in custody and is "in stable health."

Bahrain's Sunni rulers imposed martial law in March to quell a wave of Shiite-led demonstrations in the Western-allied island kingdom, the home of the US Navy's 5th Fleet.

Shiites comprise about 70 per cent of Bahrain's population. The have claimed systematic discrimination such as being blocked from top military and government posts long before protests - inspired by Arab revolts in Tunisia and Egypt - began in February.

At least 31 people have been killed and hundreds of opposition supporters, leaders and Shiite professionals such as doctors and lawyers have been arrested.

During the height of the unrest, security forces surrounded Bahrain's main state-run hospital that has treated hundreds of injured protesters and eventually took over Salmaniya Medical Complex.

The doctors and nurses were also charged with taking part in illegal rallies, harming the public by spreading false news and denying medical attention to several Sunni patients.

Another hearing in the case is set for July 6.