Financier Carl Icahn raised his bid for Nabisco Group Holdings Corp. to $22 a share from $16 as part of the continuing auction underway for the company that controls the maker of such popular snacks as Ritz crackers and Oreo cookies. Icahn, who already owns 9.5% of Nabisco Group stock, told the Securities and Exchange Commission that he planned to offer $19 in cash and $3 in two-year notes for each remaining share of Nabisco Group, or about $6.5 billion. Analysts say Icahn is probably not the only bidder, although no others have been publicly identified. Nabisco Group hired investment bankers last month to explore its options after Icahn indicated he wanted to expand his stake in the company and unseat the board so the new directors could take steps to boost the value of its shares. Icahn eventually agreed to participate in the bidding process and dropped his effort to elect his own slate to the board. But the Parsippany, N.J.-based company and the investment bankers have declined comment on the auction's progress. Nabisco Group spokesman Henry Sandbach would only say there has been significant interest. Shares in Nabisco Group rose $2.13 to close at $19.69 on the New York Stock Exchange.