SAN FRANCISCO: Google Inc's head of social networking services, Vic Gundotra, is leaving the Internet search company, he said on Thursday, three years after overseeing the launch of the Google+ social network.

Gundotra, who has worked at Google for eight years, announced the move in a Google+ post. He did not give a reason or say where he was going, but related a story about a sudden death in his extended family which made him rethink life's priorities.

"We pour our heart and soul into our work and it becomes something we love and cherish," Gundotra wrote. "But even the challenges we work on today will one day become "and thens" as we move on to the next."

Google+ marked the company's most concerted effort to catch up with Facebook Inc in the fast-growing social networking market, but it has struggled to match the popularity of the rival, which has 1.28 billion users. Gundotra said in October that 300 million users visit the Google+ web page every month.

David Besbris, a vice president of engineering in the Google+ division, has been picked to replace Gundotra whose departure is effective immediately, a source familiar with the matter said on Thursday. The person is not authorized to speak publicly about the matter and requested anonymity.

Gundotra's exit is the latest change to Google's senior leadership. Last year Android operating system boss Andy Rubin stepped aside, and in February Salar Kamangar, head of Google's YouTube video website, was succeeded by longtime Google ad executive Susan Wojcicki.

Google Chief Executive Larry Page commended Gundotra's efforts in building the company's social networking service from scratch.

"There are few people with the courage and ability to start something like that," Page wrote in a post on his Google+ profile page on Thursday, noting that the company would continue building new features for Google+.

A former Microsoft Corp manager who has appeared in a Mercedes-Benz television commercial, Gundotra was known for being an outspoken critic of rival companies.

Google has increasingly sought to position Google+ less as a social networking "stream" that competes head-on with Facebook, and more as a means of establishing a unified "user identity" system to improve Google's various Web properties. Last year, for example, Google began requiring users of its YouTube site to sign in with their Google+ identity before posting comments about videos.

Gundotra's departure and Besbris' new role were first reported by the technology blog Recode on Thursday.