Google to buy ad manager DoubleClick for $3.1 billion US

Seeking to expand its already well-honed ability to sell targeted internet advertisements, online search leader Google Inc. said it has agreed to pay $3.1 billion US in cash to buy ad-management technology company DoubleClick Inc.

The two companies announced the deal after the markets closed Friday. The boards of both companies have approved the sale, which is expected to close by the end of the year.

New York-based DoubleClick helps its customers place and track online advertising, including search ads, which Google— more successfully than its nearest search competitors, Yahoo Inc. and Microsoft Corp. — has turned into an extremely lucrative business.

Shares of Mountain View-based Google rose three cents to $466.32 USin after-hours trading. DoubleClick has been privately held since 2005.

The sellers are San Francisco-based private equity firm Hellman & Friedman, along with JMI Equity and DoubleClick management.