Sponsored Links: Abuja Nigeria,Two car bombs detonated in Nigeria's capital Friday and a third explosion hit a venue where the president was celebrating the nation's 50th independence anniversary, leaving at least seven dead following a threat from the country's main militant group. The explosions came after militants warned there was "nothing worth celebrating after 50 years of failure" in Africa's most populous nation, which is oil-rich but where most live on less than $1 a day. Friday's attacks would be among the militants' boldest yet, striking in Nigeria's capital during an event with heavy security held hundreds of miles (kilometers) from the Niger Delta region where they are based. A car bomb detonated just as a military formation began to march at Eagle Square, where President Goodluck Jonathan was on hand for the celebration. Five minutes later, a second car bomb detonated, killing at least seven people, a police officer told an Associated Press reporter at the scene. At least one of the dead was a policeman, the officer said. The officer spoke on the condition of anonymity, as he was not authorized to speak to reporters. Inside Eagle Square, an AP reporter saw a small explosive detonate before members of the military gathered there. A security agent was seen lying on the ground near that blast. The 50th independence anniversary ceremony continued without interruption, though attendees clearly recognized something had gone wrong. The Movement for the Emancipation of the Niger Delta, the main militant group in Nigeria's oil-rich southern delta, had issued a threat to journalists Friday morning. "For 50 years, the people of the Niger Delta have had their land and resources stolen from them," the statement read. "The constitution before independence which offered resource control was mutilated by illegal military governments and this injustice is yet to be addressed." Upset by the spills and the region's unceasing poverty, militants in the delta have targeted pipelines, kidnapped petroleum company workers and fought government troops since 2006. That violence drastically subsided after a government-sponsored amnesty deal last year, which provided cash payoffs for fighters and the promise of job training. However, many ex-fighters now complain that the government has failed to fulfill its promises. The militants have used car bombs before. In March, they detonated two car bombs near a government building in the Niger Delta where officials were discussing the amnesty deal, wounding two people in an attack heard live on television. In April 2006, MEND claimed responsibility for attacks on an army barracks and an oil refinery during which two people were killed. It also detonated a car bomb outside a state governor's office in December 2006. Nigeria, a member of OPEC, is one of the top crude oil suppliers to the U.S.