Shares in Africa-focused oil and gas exploration outfit Tullow Oil are at the top of the leaderboard this morning. The shares are seeing some follow-through buying following yesterday's rise. That was stoked, it seems, by an upgraded recommendation from analysts at HSBC, who upped their view on the shares to 'buy'. These experts highlighted the potential for gains in the company's stock price thanks to the "exciting" exploration program planned for this year - particularly as concerns Mauritania. A fair bit of market commentary, whether it be the Financial Times or The Daily Telegraph, is also referencing bid rumours swirling around the firm as the main reason for this morning's rise. Statoil is mentioned as a possible suitor. As of 09:23 shares of Tullow Oil are gaining 3.59% to 875.35p. AB