Nigeria issued 70 billion naira ($479.78 million) in its 20-year, 5-year and 3-year sovereign bonds at par today at its first debt auction in the second quarter of the year, Reuters quoted the Debt Management Office (DMO) as saying. Africa's top oil producer issued 10 billion naira in 20-year bonds and 25 billion naira in the 5-year and 35 billion naira in the 3-year papers, the DMO said. The bonds, which are all re-openings of previously issued papers, attracted marginal rates of 11.50 percent for the 20-year paper, 11.85 percent for the 5-year instrument and 11 percent for the 3-year paper. "The original coupon rates of 9.92 percent for the 3-year, 10.50 percent for the 5-year and 15 percent for the 20-year, will be maintained," the DMO said. "In addition, 30 billion naira (3-year) and 21 billion naira (5-year) were allotted on a non-competitive basis at the marginal rates of 11 percent and 11.85 percent respectively," the debt office said. The 20-year bond is the longest tenor debt instrument ever offered in Nigeria and was first issued in November 2008 in a bid to deepen the bond market in sub-Saharan Africa's biggest economy after South Africa. Investors demanded a total of 112.68 billion naira worth of the three instruments, but the debt office stuck to its initial 70 billion naira offer.