LinkedIn increased its planned initial public offering, valuing the largest professional social-networking Web site at more than $3 billion. It now plans to sell as much as $315.6 million of shares to expand the business, according to a regulatory filing.

LinkedIn said it is setting the IPO to include 7.84 million Class A shares at a price of $32 to $35 each, with a so- called overallotment option to sell another 1.18 million shares. It also has Class B shares, which have 10 times the voting power of Class A shares and will represent 99.1 percent of votes after the offering.