Nigeria has said that starting next month African passport holders can apply for a visa upon arrival in the country, in a move aimed at encouraging free circulation of people on the continent.The announcement was made by President Muhammadu Buhari during the Aswan Forum on peace and sustainable development that opened on Wednesday in Egypt."We in Nigeria have already taken the strategic decision to bring down barriers that have hindered the free movement of our people within the continent by introducing the issuance of visa at the point of entry into Nigeria to all persons holding passports of African countries with effect from January 2020," Buhari said."We should furthermore promote free trade within and amongst Africa and Africans especially now that we have launched the African Free Trade Area Agreement," he added. Buhari also appealed for massive investment in Africa's transportation infrastructure.  Nigeria is Africa's biggest economy and market with some 190 million inhabitants. Along with Benin, it was one of the last nations to join the new African free trade zone in July.The goal is to become the world's largest free trade zone by cutting trade tariffs and barriers for 1.2 billion people.    The new market is set to become active in 2020 as negotiations continue to manage its progressive implementation.    In contrast to its aims of a free flow of trade, Nigeria in late August and "until further notice" closed the borders with neighbouring countries - highly dependent on the economic giant - to block contraband products such as petrol and rice.