DI KHAN: An explosion that happened close to a police vehicle at Tank Adda here claimed the lives of four bystanders and injured fifteen police officers and civilians. The car carrying members of the special team was attacked, police said, by unidentified militants. The unidentified militants started shooting at the police officers stationed at the hospital as soon as the injured were brought there.After securing the area with barricades, the police and security personnel began their search. It should be mentioned that the police van was targeted while the elite force squad was being transported from Dera Ismail Khan to the Takwara checkpoint.