The tiny Gulf state's High Criminal Court also revoked the citizenship of two of those convicted, terror crime prosecution chief Ahmed al-Hammadi said in a statement published by the official BNA news agency.
"The convictions relate to attempted murder of policemen, using and possessing explosives and weapons, rioting, and receiving and providing explosives," Hammadi said.
The group were also found guilty of "training in order to commit terrorist crimes," he added.
It did not identify the defendants or give detailed information on the convictions.
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Attacks against police are common in Sunni-ruled Bahrain, a Western ally and home to the US Fifth Fleet.
The kingdom has a majority Shiite population and lies across the Gulf from Iran.
It has been rocked by a Shiite-led uprising since February 2011, with demands ranging from a constitutional monarchy to overthrowing the ruling Sunni dynasty altogether.