ABUJA (Reuters) - A more flexible foreign exchange policy will help Nigeria's economy, which has been hit by a slump in oil revenues, President Muhammadu Buhari said, backing a recent move by the central bank.

"The central bank has moved to introduce a greater flexibility in our exchange rate policy. These actions are a down payment on our people's ability to succeed," Buhari wrote in an essay in The Wall Street Journal, according to the newspaper's website.

He gave no details how the policies would be implemented, saying only that Nigeria needed to boost supplies of foreign exchange.

"This requires radically increasing exports and productivity and improving the investment climate and ease of doing business," Buhari said.

Last month the central bank said it would introduce a more flexible exchange policy, but it has given no guidance how this will be done.

A slump in oil prices has dried up oil revenues on the official channels, knocking down the naira on the parallel market while the bank has kept the official rate stable.

Buhari also said the government planned to lower taxes on small businesses and give priority development funding to sectors such as agriculture.

Buhari's office confirmed the authenticity of the comments on its Twitter account late on Monday.

(Reporting by Ulf Laessing; Editing by Leslie Adler)