Time Warner shares are surging on confirmation that Twenty-First Century Fox has offered an $80 billion bid, a proposed deal Time Warner later rebuffed. The owner of movie studio Warner Brothers and popular networks TBS and CNN said it had rejected the cash-and-stock deal after deeming the offer too low. Time Warner's board also cited the "considerable strategic, operational and regulatory risks" as reason to turn down a combination. Negotiations have reportedly been in the works since June with Fox boss Rupert Murdoch keen on making a deal work. The offer represented a 25% premium to Time Warner shares at the time, or around 12.6 times EBITDA. TheStreet's Keris Lahiff reports from New York.