NEW YORK AP-Lehman Brothers Holdings Inc. on Monday said it will raise $6 billion in new capital to shore up its balance sheet after saying it expects to post an unexpectedly large second-quarter loss of nearly $3 billion.

Shares of the nation’s fourth-largest investment bank fell about 9 percent amid mounting concerns about its exposure to the mortgage market. Analysts were quick to react to Lehman’s announcement, with credit rating agency Moody’s Investors Service lowering its outlook on the firm.