Prosecutors allege that Alison-Madueke, Nigeria’s oil minister from 2010 to 2015 and a former president of OPEC, accepted bribes from oil-industry figures seeking lucrative government contracts, including cash and payments covering personal expenses and luxury purchases in London. The case forms part of a long-running international corruption probe that began after her arrest by UK authorities in 2015 and has also triggered asset-recovery proceedings in the United States, where more than $52 million in alleged corruption proceeds have already been repatriated to Nigeria.