ABUJA, April 6 -- The World Bank, International Monetary Fund (IMF) and African Development Bank (AfDB) have endorsed Nigeria's new Gross Domestic Product (GDP) of approximately 509.9 billion U.S. dollars released on Sunday and placing the West African country as the biggest economy in Africa, said an official who spoke for the three financial institutions.

According to the figures released by the National Bureau of Statistics after a rebasing, Nigeria surpassed South Africa with a 2013 rebased figure of 370 billion U.S. dollars, to emerge as Africa's biggest economy.

The new figures show that the biggest oil producer in Africa climbed to the 26th largest economy in the world.

"I speak on behalf of three development partners, namely the World Bank, African Development Bank and the International Monetary Fund, in first congratulating the National Bureau of Statistics on their announcement today (on Sunday) of the rebased GDP figure for the Nigerian economy," said Gene Leon, country representative of the IMF.

"Let me state that we endorse this wholeheartedly and we support Nigeria in this regard," said Gene Leon, country representative of the IMF, adding the economic policies of Nigeria could be better and more correctly targeted based on the updated information than it could have been, using the outdated information.

The GDP index is the total value of a country's goods and services over a period of time. Rebasing is carried out to give the most up-to-date picture of an economy as possible. According to the IMF, countries are supposed to rebase their GDPs after every five years, but Nigeria's was last computed in 1999 when there was limited growth in most economic sectors.

The new calculation, released by the bureau of statistics, now includes previously uncounted industries like telecoms, information technology, music, on-line sales, airlines, and film production.