Egyptian billionaire Naguib Sawiris has resigned as chief executive officer of Orascom and his deputy Tamer El Mahdi has been nominated as his successor, the company said on Sunday, without explaining his decision. "Naguib Sawiris has submitted his resignation from his position as CEO effective January 1st, 2017," Orascom Telecom Media and Technology Holding (OTMT) said in a statement. Orascom has holdings in media, technology and cable businesses, but under Sawiris has sought to move further into the financial sector by creating a major investment firm. "Mr. Sawiris will continue to assume all responsibilities of his current position until the appointment of the new CEO is completed and registered with regulatory authorities," Orascom added.