Amnesty International is calling for an investigation into the death of a prominent imprisoned dissident in the oil-rich West African nation of Equatorial Guinea. The 51-year-old Julio Obama Mefuman, who is also a citizen of Spain, had been serving a 60-year-jail sentence. In 2017, he and another dissident had been kidnapped in South Sudan and brought to Equatorial Guinea to be imprisoned. Just two weeks ago, Spain announced it would investigate the circumstances of how the men were seized. Equatorial Guinea has been led by the U.S.-backed dictator Teodoro Obiang Nguema Mbasogo since 1979. He is the longest-serving president in the world.