A subsidiary of Japan's second-biggest trading company, Mitsui & Co has acquired a stake in an exploration area in waters off Ghana from Africa-focused oil and gas explorer Afren Plc .

With the deal, UK-based Afren, which is also the operator of the project, will reduce its stake to 68%, and Mitsui will gain a 20% stake in the Keta block, pending Ghana's approval.

Ghana National Petroleum, with a 10 percent stake, and Gulf Atlantic Energy, with a 2 percent stake, are also stake holders in the exploration area, which is located about 40 km off the eastern coast of Ghana and covers about 5,500 square km.

Japan's state-run Japan Oil, Gas and Metals National Corp has agreed to provide 75 percent of the funding for Mitsui in the project, which will be the first exploration project in Ghana for a Japanese firm.