QUETTA, Pakistan—A suicide bomber detonated his explosives Sunday near a security checkpoint in restive southwestern Pakistan, killing at least three paramilitary troops and wounding 15 others, police said. Senior police officer Azhar Akram said the attacker had walked toward the checkpoint manned by the paramilitary Frontier Corps on Quetta-Mastung Road, some 25 kilometers (15 miles) south of Quetta, the capital of Baluchistan province. He said body parts were found at a distance from the security post after the bombing. Akram said some of the wounded were in critical condition and the death toll could rise. Banned terrorist group Tehrik-e Taliban Pakistan (also Tehreek-e-Taliban Pakistan or TTP), also known as the Pakistani Taliban, claimed responsibility for the morning attack. It was the first time TTP claimed an attack on Pakistani security forces since the Taliban—a separate organization—took control of neighboring Afghanistan. Baluchistan has also seen a low-level insurgency by Baluch separatist groups …