Yahoo Inc has been given U.S. antitrust approval to buy BlueLithium, the Federal Trade Commission said on Wednesday.

U.S. antitrust authorities decided the deal posed no antitrust concerns. The transaction was listed in a daily notice of such approvals issued by the FTC.

Yahoo announced in September that it would buy BlueLithium, the fifth-largest U.S. online ad network for $300 million in cash.

A series of recent deals have consolidated the online advertising market. Others include Google Inc's pending purchase of Doubleclick, Time Warner Inc's purchase of Tacoda and Microsoft Corp's purchase of aQuantive Inc>.

(Reporting by Diane Bartz)