Japanese conglomerate Toshiba said CEO Nobuaki Kurumatani had resigned Wednesday, as a potential $20 billion takeover by CVC Capital Partners became messy with new bidders said to be in the mix.

Shares in Toshiba jumped 7% higher to 4,900 Japanese yen ($44.82), not far off the 5,000 yen per share level reportedly offered by CVC Capital.

Toshiba Chairman Satoshi Tsunakawa will become chief executive, the company said in a statement, with the board slated to hold a meeting later Wednesday to review options.

Kurumatani drew fire over the bid from CVC, his former employer, and strained relations with shareholders over the CVC bid.

Private equity giant KKR & Co has been mentioned as a possible bidder, along with Canada's Brookfield Asset Management, according to news reports.

A representative for KKR Japan declined to comment. Brookfield did not immediately respond to a request to comment.