A Bahrain court has sentenced 17 people to 15 years in prison after convicting them of trying to kill four policemen with a homemade bomb during political unrest last year. The attackers planted the bomb in a roadblock formed of tyres, palm tree trunks and garbage bins, and detonated it when a police patrol approached, prosecutor Mamdouh al Maawdaas said. The four policemen were seriously hurt and burned during the attack in April 2012.