Police have arrested four more suspects linked to a high-profile knifepoint robbery in Hong Kong following a joint cross-border operation, though the stolen gold bars remain missing.The robbery occurred early on Thursday at Hong Kong International Airport’s car park 3, where a 36-year-old local man, carrying a backpack loaded with six gold bars weighing about 6kg and valued at HK$7 million, was ambushed by three knife-wielding assailants.The attackers slashed his arms and legs before escaping...