Japan's Toshiba nosedived nearly 26 percent on Thursday, marking a fifth consecutive session decline, after credit downgrades from both Moody's and S&P Global Ratings. Moody's downgraded Toshiba to CAA1 on Wednesday, and placed its ratings on review for further downgrades over concerns about the sustainability of the Japanese firm's near-term liquidity and its corporate governance framework. S&P Global Ratings also lowered its ratings for Toshiba, downgrading its long-term corporate credit to B- from B, and its senior unsecured debt ratings to B+ from BB-.