(Telecompaper) MTN Nigeria has issued a trading caution to shareholders but denied any improper repatriation of funds, after the Central Bank of Nigeria (CBN) ordered the return of USD 8.1 billion it alleges the operator illegally moved out of the country. MTN said it received a letter on 29 August from CBN, alleging that Certificates of Capital Importation (CCIs) issued in respect of the conversion of shareholders loans in MTN Nigeria to preference shares in 2007, had been improperly issued.