Three bomb disposal experts were killed and 20 colleagues wounded on Friday as a roadside device they were trying to disarm exploded at their police station in central Iraq, a police official said. Police found the device in downtown Diwaniyah and took it to their station but it exploded as they tried to disarm the bomb, the official said. Iraqis are to vote in provincial elections on Saturday, the country's first vote since 2005, amid fears that insurgents could try to disrupt polling despite heavy security.