The Central Bank of Nigeria says it has uncovered what it describes as ”a highly sophisticated plot to defraud it by some criminally minded elements”.

The bank did not reveal the nature and volume of the fraud, but said it has been aborted.

It also said it has suspended it’s key personnel involved in the transaction, hinting that it must a great fraud involving the transfer of huge dollars in its reserve.

The Nation newspaper said the amount involved was $400million and that a deputy governor of the bank was among the CBN staff suspended.

“Although preliminary investigations so far have not revealed accomplices within the CBN, management has decided to place all key personnel involved in the transaction on suspension. This is to ensure a full and unfettered investigation, ” said Isaac Okoroafor, the bank’s acting director of communication.

Okoroafor said the aborted fraud has been reported to relevant authorities.

Fraud is not uncommon in Nigeria’s banking system. But it is rare that fraudsters will target the apex bank.

In February, the CBN reported that various electronic payment systems that it deployed have helped curb incidences of fraud in banking transactions in 2015.

The director of Banking and Payments System Department of the CBN, Dipo Fatokun, said the actual loss as a result of fraud in bank transactions dropped from N6.2 billion recorded in 2014 to about N2.3 billion in 2015.

Mr. Fatokun said while cases of attempted fraud fell from N7.8 billion to N4.4 billion in 2015, the volume of such cases jumped astronomically from 1,461 to 10,743 during the same year.