A suicide bomber detonated an explosives-laden vehicle near a railway track as a passenger train travelled through the south-western Pakistani city of Quetta, killing at least 23 people and wounding more than 70 others, officials have said. The force of the explosion on Sunday caused two of the train cars to overturn and catch fire, sending thick black smoke into the air, according to footage shared online. The attack happened in an area where security forces are usually stationed, badly damaging several nearby buildings and smashing more than a dozen vehicles parked along the road, according to witnesses and images circulating on social media. Doctors at local hospitals said they had received the wounded, with 20 in critical condition. Three security officials told the Associated Press on condition of anonymity that the bodies had been transported to hospitals after the attack. Doctors at hospitals in Quetta said they had received the wounded, with 20 in critical condition.…