The naira also weakened across the board on the forwards market , with the currency quoted at 472 to the dollar on the one-month contract on Thursday.
The currency weakened to a low of 461 to the dollar on the official market on Wednesday.
"We know that at the end of year (central bank) adjusts rates," a currency trader at a local bank said.
"They have done it every year for the last two years," the trader said, adding that the exchange rate could hit 465 to the dollar by the end of the year.
The naira has fallen to successive lows across both the official and black markets due to dollar scarcity since last year after the central bank intervened to ease pressure on the spot market, where the naira has been trading within a range.
As the currency weakens, demand increases on the official market, traders said. The unit has been flat at 740 naira on the parallel market .