Professional networking site LinkedIn's quarterly revenue more than doubled, as the company sets off to prove it can fulfill the promise of its splashy IPO and rich valuation.

It said second-quarter revenue increased 120 percent to $121.0 million, surpassing an average forecast of $104.73 million, according to Thomson Reuters I/B/E/S.

LinkedIn -- used by professionals seeking jobs or contacts and companies searching for qualified applicants to fill slots -- is the first prominent U.S. social networking site to make its public debut. Shares of the company more than doubled its IPO price during its first day of trading on the New York Stock Exchange in May -- whetting the appetite of investors for a Facebook IPO.

(Reporting by Edwin Chan and Jennifer Saba; Editing by Gary Hill)