The unit closed at 191.10, a new record low against the U.S. dollar, compared with Friday's record low close of 190.60 naira. One dealer traded the naira at a one-off rate of 194.10 during mid-day session.
The currency had initially gained 1.66 percent to 186.80 naira after the central bank and two oil companies sold dollars to lift the naira, before it then slipped into negative territory.
The naira has hit a string of record lows as dollar liquidity on the interbank forex market thins out amidst a collapse in the price of oil, Nigeria's main export.
Dealers said Total offered to sell $80 million to some lenders on Monday while Shell sold an undisclosed amount of dollars, to buy naira for their local operations.