shanghai china big four state-owned bank stop provide financial service new north korean clients accord branch staff amid u.s. concern beijing tough enough pyongyang repeat nuclear test tensions unite state north korea ratchet sixth powerful nuclear test conduct pyongyang sept. prompt unite nations security council impose sanction tuesday chinese bank come scrutiny role conduit fund flow china increasingly isolate neighbor china construction bank ccb 601939.ss completely prohibit business north korea say bank teller branch northeastern province liaoning ban start aug. 28 teller say frustrate china do rein north korea trump administration mull new sanction july small chinese bank firm business pyongyang two senior u.s. officials tell reuters person answer customer hotline world large lender industrial commercial bank china ltd icbc 601398.ss say bank stop open account north koreans iranians since july 16. person explain answer question measure take large chinese bank begin early end last year dandong city branch china international lender bank china ltd boc 601988.ss stop allow north koreans open individual business account say boc bank teller decline identify exist north korean account holders could deposit remove money account boc bank teller say agricultural bank china ltd agbank 601288.ss teller branch dandong northeastern chinese city border north korea say north koreans could open account teller provide detail official representatives boc icbc ccb agbank could reach comment bank dandong microscope tensions rise give proximity north korea june unite state accuse bank dandong small lender launder money pyongyang attempt slowly choke flow fund north korea come unite state sanction chinese industrial machinery wholesaler say act behalf pyongyang bank already sanction unite nations support proliferation weapons mass destruction chinese wholesaler find operate 25 account bank china although measure place bankers question well rule would enforce chinese lenders experience high-profile failures police money-laundering recent years face allegations bankers complicit movement illicit fund ask whether able enforce new rule question ask tight know-your-client check say senior corporate banker bank china decline identify sensitivity matter always hole say china 's big bank halt service north koreans tellers say