Manama: A Bahrain court sentenced 17 people to 15 years in prison on Sunday 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, state news agency BNA quoted prosecutor Mamdouh Al Maawda as saying. The four policemen were seriously hurt and burned during the attack in April 2012, BNA reported. Bahrain has been plagued by sometimes violent street protests since anti-government protests erupted in early 2011. Also on Sunday, a group of people attacked a diesel tanker with Molotov cocktails, BNA quoted police as saying. Civil defence personnel extinguished the flames before they reached the diesel cargo. Bahrain held on Sunday its eighth round of national talks aimed at helping heal the wounds that have scarred the nation. However many believe the dialogue is turning into a maelstrom of deep mistrust. Two political blocs representing the opposition and Al Fateh, the parliament and the government have been sitting together since February 10 to help charter a plan that will initially rebuild confidence among the various communities and help the country end a political deadlock. However, more than one month into the talks, no agenda has been set and accusations of lack of cooperation, mainly through the media, have become the main headlines. Al Fateh has charged that the coalition of the opposition was not helping with the dialogue by insisting on issues that had been settled, mainly whom the participants represented. However, the opposition said that there had been no final agreement on the format of the dialogue, giving it and the other participants the right to add new items.