Nigeria’s total debt rose to 12.1 trillion naira ($60.8 billion) as of March 2015, up from 11.2 trillion naira at the end of December 2014, the Debt Management Office (DMO) said.

The DMO said on its website that foreign debt stood at $9.46 billion at the end of March, equivalent to about 15 percent of total debt and down from $9.71 billion at the end of 2014.

Nigeria said in 2013 it wanted to increase the amount it borrowed overseas to 40 percent of all debt over a three-to-five year period to tap into loose monetary policy in advanced economies.

But as oil prices plunged last year, government revenues slumped, leaving Abuja struggling to pay bills including state salaries. The currency has also come under intense pressure.

Nigeria’s states are now in debt to the tune of 658 billion naira, the governor of Zamfara state said last week.

Investors are worried domestic debt has risen sharply since the end of March, and concerns about government finances, as well as the slide in the naira, are hitting markets.

The yield on the 5-year bond, the most liquid issue, rose to 14.95 percent on Tuesday, up from 14.71 percent a week ago.

Nigeria’s former finance minister said at the start of May that the government had already used half the borrowing allowance it had budgeted for as lower oil prices reduced revenues.

Abuja’s funding problems and the naira’s weakness on the black market are fuelling market concerns that more domestic bonds may have to be sold, raising the cost of borrowing.

Nigeria rebased its gross domestic product statistics last April, almost doubling the size of its economy to more than $500 billion, Africa’s biggest. However tax collection as a percentage of revenue is a paltry 6 percent.