Nigeria expects to spend 6.31 trillion naira ($15.1 billion) on servicing its domestic and foreign debt next year, much higher than the 3.69 trillion set aside for this year, a finance ministry document showed on Wednesday.

President Muhammadu Buhari's government has borrowed heavily to fund capital projects, including roads, rail and bridges, saying this will boost economic growth.

A "Budget Call Circular" to guide federal ministries on planning next year's budget showed that 3.3 trillion naira would go to servicing local debt, 1.814 trillion towards external debt, and the balance to finance central bank borrowing and retire maturing loans.

By spending more on debt servicing, Africa's biggest economy is leaving less money for health and education. Under the budget proposal, the federal health and education ministries will be allocated a combined 154 billion naira ($369 million) next year.

In the first four months of this year, Nigeria spent $4.7 billion to service its debt, higher than public revenue.

Nigeria is not generating enough revenue, analysts say, while its spending keeps growing, which means the country of more than 200 million people will have to continue borrowing to repay debt.

$1 = 417.47 (Reporting by MacDonald Dzirutwe; Editing by David Holmes)