TOKYO (Reuters) -Toshiba Corp CEO Nobuaki Kurumatani resigned on Wednesday amid controversy over a $20 billion buyout bid from CVC Capital Partners, while its shares rose on reports that KKR & Co and Brookfield are also planning offers. Satoshi Tsunakawa, who led the company before Kurumatani and until Wednesday was chairman, will once again assume the helm. Kurumatani, CEO for three years, had been under fire over the bid from CVC, his former employer, as well as facing allegations that investors were pressured before a shareholder meeting to support desired board nominations. CVC’s offer to take the Japanese conglomerate private and retain incumbent management was perceived by some in the company as designed to shield Kurumatani from activist shareholders, Toshiba sources have said. Those shareholders have successfully pushed for an independent investigation into the allegations, sources familiar with the matter have said. CVC was planning to team up with U.S. firm Bain Capital for its buyout offer, the Nikkei newspaper reported following Kurumatani’s resignation. A representative for Bain declined to comment. CVC also declined to comment. CVC’s proposal had sparked a strong backlash from Toshiba managers, prompting them to lobby against it to the government, said one of the sources, who declined to be identified due to the sensitivity of the matter. “Tsunakawa has the trust of various stakeholders,” Toshiba Board Chairman Osamu Nagayama told a news conference. Toshiba said Kurumatani was stepping down to “recharge” after achieving his plan to revive the conglomerate following an accounting scandal. Reuters was not immediately able to reach him for comment. People familiar with matter said two board members had told Kurumatani they planned to oust him due to his slumping support among shareholders and staff, and that the CVC offer had only accelerated the move. Nagayama said CVC’s April 6 proposal was unsolicited, lacked substance and required cautious consideration. He noted that a law which restricts foreign ownership in Japanese companies with important technology would have to be taken into account. Toshiba would consider setting up an independent committee of external directors after receiving a formal proposal from CVC, he added. Tsunakawa, who has a reputation for being on better terms with Toshiba’s large activist shareholder base, said the company needed to rebuild trust with investors and acknowledged there was room to improve governance. The Toshiba shareholder vote last month for an independent probe was a watershed victory for corporate governance in Japan, marking the first time that a motion by an activist shareholder has won approval at a major company. Both Nagayama and Tsunakawa suggested current management did not intend to be in place for too long.