Nigeria lost about $3bn (£2.4bn) from 97 tonnes of gold illegally smuggled out of the country in the seven years up to 2018, President Muhammadu Buhari has said.
He made the disclosure on Thursday in his speech during the official presentation of gold bars produced thanks to a presidential initiative to help small-scale miners.
The initiative, launched last year to reform the sector, would support jobs especially for artisanal miners, creating about 250,000 jobs from improved gold mining operations, the president said.
The country also stood to earn $500m annually in royalties and taxes, he added.
Mr Buhari himself was presented with a locally produced 12.5kg gold bar worth $691,000, which was purchased by the central bank.
His special assistant tweeted about what the presidency says is a "milestone moment".
"This means that the Central Bank will be purchasing gold that has been mined, processed and refined under the Presidential Artisanal Gold Mining Development Initiative for use as part of Nigeria’s external reserves," a statement said.