Police arrested Friday a gang of thieves who spied on and stole from bank customers who extracted large sums of money from their accounts. According to police, the gang consisted of persons of African nationality, and were caught after undercover officers kept them under surveillance and observed them monitoring the activities of customers at a series of bank outlets around the city. The group was caught in the act of stealing a case from a customer who had been followed by the gang after they observed him withdrawing a large amount of money from a bank. Investigators were told that the gang did not attack their targets physically but limited their activities to snatching bags. The arrests follow the detention on Wednesday of seven Africans who also targeted bank cusomers who had arrived by car and followed them to other areas of town before robbing their vehicles after their targets had parked to conduct other business.