ABUJA- Nigeria's naira inched down against the dollar on Monday, having recently weakened in the official market in a move suggesting the central bank may be trying to unify its numerous exchange rates - a system for which it has received widespread criticism.

The naira closed at 411.67 to the dollar after falling to 419 at one point. It had closed at 411.25 naira on Friday after hitting a record low of 419.50 as the currency was allowed to weaken.

Since last July the naira had been trading between 380 and 381 to the dollar on the official market, backed by the central bank.

The central bank has been trying to unify its exchange rates and boost the dollar supply through direct interventions.

The country has been operating a system of multiple currency rates, which has frustrated businesses and prompted calls from the World Bank for its rates to be unified to help attract investment.

Rising dollar demand has put pressure on the naira as providers of foreign exchange, such as offshore investors, exited after the COVID-19 pandemic triggered a fall in global prices for oil - Nigeria's biggest export.

Only two quotes were shown for the currency on Monday, after two late trades. Volumes were not shown for those trades, however.

(Reporting by Chijioke Ohuocha; Editing by Kevin Liffey and Hugh Lawson) ((chijioke.ohuocha@thomsonreuters.com; +234 703 4180 621; Reuters Messaging: chijioke.ohuocha.thomsonreuters@reuters.net))