Militants detonated a car bomb at a police checkpoint in Bannu, northwestern Pakistan , and opened fire on officers, killing at least 15 people, authorities said Sunday. The attack took place late Saturday in the Fateh Khel area. Images from the scene showed the checkpoint reduced to rubble, with bricks, charred debris, and mangled vehicles scattered across the area. "Last night in the Fateh Khel area of Bannu, a suicide bomber rammed an explosives-laden vehicle into a police checkpoint, after which multiple militants entered the post," Bannu police official Muhammad Sajjad Khan said. He added more than 100 militants took part in the attack.  Officials said the car was filled with explosives when militants rammed it into the post Image: Ehsan Khattak/REUTERS Deadly checkpoint assault An officer, speaking on condition of anonymity, said that other law enforcement personnel had been sent to help the police but that the terrorists had ambushed them, causing some of the casualties.…