By Reuters Staff (Adds Sasol comment) JOHANNESBURG, June 27 (Reuters) - State-owned energy companies from South Africa and Mozambique have exercised their rights to buy the 30% stake in the ROMPCO natural gas pipeline that Sasol is selling, the companies said on Sunday. Petrochemical firm Sasol said last month it was selling the stake in the ROMPCO pipeline from Mozambique to South Africa to a consortium of investors including Reatile Group for an initial amount of 4.15 billion rand ($293 million). But that deal was subject to pre-emptive rights on the shares held by existing shareholders iGAS, a subsidiary of South Africa’s Central Energy Fund, and Companhia Moçambicana de Gasoduto (CMG), a subsidiary of Mozambique’s Empresa Nacional de Hidrocarbonetos.