Banking giant Citibank was almost caught out by a group of fraudsters who tried to swindle $27m out of the banking group using the infamous “419” scheme, a court has been told.

Paul Gabriel Amos, a Nigerian citizen who lived in Singapore, is on trial in the US charged with conspiracy to commit bank and wire fraud after attempting to claim the huge sum from the National Bank of Ethiopia.

It is alleged that Amos and a number of fellow scammers instructed Citibank to wire funds directly from the National Bank of Ethiopia to a series of accounts that they controlled.

The fraud was uncovered after several banks where the conspirators held accounts returned money to Citibank, claiming they had been unable to process the transactions. An official of the National Bank of Ethiopia had also vetoed the transactions, according to a complaint signed by an F.B.I. agent, Bryan Trebelhorn.

The infamous advance fee fraud scam, also known as the “419” scam due to the criminal code in Nigeria, where the scam is considered to originate, traditionally target individuals through emails with the promise of financial reward for performing certain tasks, lottery wins or promises of romance.

The victims are eventually coerced into transferring large sums of money to the fraudsters, at which point the scammers end communication.

A Citigroup spokeswoman told the New York Times: “We have worked closely with law enforcement throughout the investigation and are pleased it has resulted in this arrest. Citi constantly reviews and upgrades its physical, electronic and procedural safeguards to detect, prevent and mitigate theft.”

A spokesman for the Ethiopian Embassy in Washington said, “We are aware of this unfortunate story.” He said the embassy was not involved in the legal proceedings, and declined further comment.

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