Nigeria's Central Bank has suspended 16 banks from trading in foreign currency for one year after uncovering illegal foreign exchange transactions.

Officials with the Central Bank said today (Friday), the banks had been buying foreign currency cheaply on the official exchange market and selling it at inflated prices on the black market. They say the suspensions are the result of an investigation into 21 of the nation's banks.

The Central Bank officials say the crack down is an effort to sanitize the Nigerian banking system and shift its focus away from foreign exchange trading and into other services .