Diamond Bank PLC said the Central Bank of Nigeria has debited from its accounts with the regulator a 250 million Nigerian naira fine that the lender was told to pay following an investigation into foreign exchanges remittances carried out on behalf of MTN Nigeria Communications Ltd., a unit of South African telecommunications firm MTN Group Ltd.

The bank said it will continue to engage and cooperate with the central bank in the case while reaffirming that it carried out the transactions in full compliance with all rules and guidelines.

"Please note that the payment of this fine does not impact our capacity to offer normal banking services, nor our clients' ability to access these, including transactions that have to do with capital importation," Diamond Bank added.

The central bank also debited 2.4 billion naira from the accounts of Standard Chartered PLC, Reuters reported, citing two unnamed sources. The U.K.-based lender reportedly denied any wrongdoing.

The central bank had ordered South African telecommunications firm MTN and four banks to return roughly $8.1 billion it said MTN illegally transferred abroad in violation of foreign exchange regulations. The regulator fined StanChart, Diamond Bank, U.S.-based Citibank NA and Nigeria's Stanbic IBTC Holdings PLC a combined 5.65 billion Nigerian naira.

As of Sept. 7, US$1 was equivalent to 359.80 Nigerian naira.