The 55.22-carat ruby found by a Dubai-based firm was purchased by an anonymous telephone buyer at Sotheby's auction in New York
With oil prices above $120 a barrel, Vice President Goodluck Jonathan said the lost oil costs Africa's most populous country 8 billion naira ($67.8 million) per day.
"It is very disturbing that a few weeks ago, for the first time, Nigeria's daily oil production dropped to below 1.8 million barrels per day," Oil Minister Odein Ajumogobia told reporters on behalf of the vice president.
"We all agree that the issue in the Niger Delta needs to be urgently addressed."
Kidnappings, pipeline bombings and oilfield raids in the delta, the heartland of Nigeria's oil production, have slashed a fifth of the OPEC member's production since early 2006 and helped push international oil prices to record highs.
The militants say they are fighting for a greater share of the region's oil wealth after decades of neglect, but the breakdown of law and order in the delta has allowed criminal gangs to thrive by kidnapping for ransom and stealing crude.
President Umaru Yar'Adua took office more than a year ago pledging to address the root causes of the instability, but plans for a long-delayed peace summit have fallen into disarray and criminality in the region appears to be increasing.
The Movement for the Emancipation of the Niger Delta (MEND), the country's most prominent militant group, threatened on Monday to attack foreign workers with construction firm Julius Berger JUBR.LG if it does not halt operations in the capital Abuja within a week. [nL4243777]
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Ministry expresses its sincere sympathies to the government and people of the French Republic and to the families of the victims of the heinous crime