A Bahrain court sentenced 17 Shiite activists to 15 years in prison on Sunday after convicting them of the attempted murder of four policemen in a bomb attack in April last year, a judicial source told AFP.

The defendants were found guilty of detonating a roadside bomb in the Shiite village of Aker that wounded four members of a passing police patrol, the source said.

Sunni-ruled Shiite-majority Bahrain has seen two years of political unrest linked to opposition demands for a consitutional monarchy that has killed at least 80 people, according to human rights watchdogs.

The small but strategic island state lies across the Gulf from Iran and is home to the US Fifth Fleet.