GHAZNI: An explosion killed four Afghan police including a district chief on Thursday as they attempted to defuse a roadside bomb in the restive south. The blast occurred as Mohammad Qasim and his team attempted to defuse one of two roadside bombs found in Waghiz district of Ghazni province. "They defused the first bomb and while they were trying to defuse the second one nearby, it detonated and killed them," provincial spokesman Shafiq Nang told AFP.