(Recasts on resignation) TOKYO, April 14 (Reuters) - Toshiba Corp CEO Nobuaki Kurumatani resigned on Wednesday amid controversy over a $20 billion buyout bid from CVC Capital Partners and the conglomerate’s shares surged on reports that more suitors were planning offers. Toshiba Chairman Satoshi Tsunakawa will become chief executive, the company said in a statement. The statement gave no reason for the resignation but Kurumatani has come under much fire over the bid from CVC, his former employer, and his testy relations with the company’s large activist shareholder base. A news conference is planned at 12.30 local time. (0330 GMT) His departure could upend CVC’s offer last week to take Toshiba private at a time when rival suitors are said to be weighing bids. Private equity giant KKR & Co is considering a buyout offer that would exceed CVC’s, the Financial Times has reported, citing several people briefed on the plans. Canada’s Brookfield Asset Management Inc is in the preliminarily stages of exploring an offer, Bloomberg News reported, citing a person with knowledge of the matter said. A representative for KKR Japan declined to comment. Brookfield did not immediately respond to a request to comment. Sources familiar with the matter have said a CVC takeover would shield Kurumatani and other managers from pressure from activist shareholders. The activist shareholders have successfully pushed for an investigation into whether management pressured investors to support their decisions. The sources declined to be identified due to the sensitivity of the matter. Shares in Toshiba were trading 7% higher at 4,900 yen, not far off the 5,000 yen per share level reportedly offered by CVC Capital. (Reporting by Makiko Yamazaki, Sakura Murakami and Chang-Ran Kim; Additional reporting by Kane Wu; Editing by Edwina Gibbs)