Angolan President Jose Eduardo dos Santos, who has been in power since 1979 and is one of Africa's longest-ruling leaders, will not stand for re-election at national polls due to be held next year, a ruling party document showed on Friday, according to Reuters. Joao Lourenco, the defence minister and vice president of the MPLA party, was approved by its key decision-making body as its flag bearer to succeed Dos Santos. Angola, a member of OPEC and Africa's second largest oil exporter after Nigeria, has been hit hard by the slump in global crude prices. Oil export revenues account for more than 90 percent of foreign exchange revenues.