Traders said the bank, which has been selling dollars regularly to prop up the currency, sold around $1.5 million towards the close of Monday's trade after the market was open for nearly four hours with no deals.
The naira was quoted at 455 to the dollar on the black market on Monday, firmer than 460 at its previous session, as international money transfer operators had started to sell dollars to retail currency outlets.
The currency had weakened to a record low of 495 per dollar on the black market last month.
The bank held a dollar forward auction last Friday to clear a backlog of demand from airlines, manufacturers and other companies, as the country's currency crisis deepened. Result of the auction was yet to be published, traders say.