A Bahraini special court has upheld life jail sentences served on seven Shiite opposition leaders convicted of plotting to overthrow the regime in the Gulf kingdom, BNA official news agency said.

Jail sentences against seven other activists, ranging between two to 15 years and including Sunni opposition leader Ibrahim Sharif, were also upheld by the national safety appeals court, it said quoting military general prosecutor colonel Yusof Fulaifel.

Seven others, one sentenced to life in jail and the remainder to 15 years, remained at large and had not appealed their sentences.

The appealed verdicts will go to a civil court of cassation for a final decision.

The eight activists sentenced to life include Hassan Mashaima, head of the Shiite opposition Haq movement, and Abdulwahab Hussein, who leads the Shiite Wafa Islamic Movement, as well as Shiite human rights activist Abdulhadi al-Khawaja, who is also a Danish citizen.

Activist and Haq member Abduljalil al-Singace, who was released in February after six months in jail, was also sentenced to life.

The other four are Mohammed Habib al-Muqdad, who holds a Swedish passport; his cousin Abduljalil al-Muqdad and Saeed Mirza, both of whom are Wafa members, and Said Abdulnabi Shihab, who was sentenced in absentia.

Sharif, the Sunni leader of the Waed secular group, who played a prominent role in month-long protests for democratic reform that were crushed in March, received a five-year sentence.

Sharif and other leading opposition figures were arrested amid the Sunni authorities' crackdown on the protests led by the islands' Shiite majority.

Nine of the defendants had been in custody on similar charges in the past before being set free under a royal pardon in February aimed at calming the protests.

Scores more activists are facing trial on charges linked to the protests in a semi-martial court set up under a "state of national safety" decreed by King Hamad a day before protesters were evicted from a Manama square in mid-March.

Authorities backed by troops that rolled into Bahrain from fellow Gulf nations quelled the protests while security forces set about arresting hundreds of activists, as well as doctors, medics and teachers accused of backing protesters.

Bahrain's interior ministry said 24 people, including four policemen, were killed in the unrest. The opposition puts the death toll at 30.