African governments must ensure transparency and accountability in the management of natural resources, including oil, to generate revenue for growth through diversifying economies, a United Nations official told delegates at an industrial policy conference in Ghana. 'African leaders must have bold visions and good planning,' Kandeh K. Yumkella, the Director-General of the UN Industrial Development Organisation (UNIDO), told delegates attending the two-day conference in Accra entitled 'Competitiveness and Diversification: Strategic Challenges in a Petroleum-Rich Economy'.