Internet firm Google's online social networking service 'Google Plus' has crossed 40 million users mark since its launch in June.

Google Plus now has attracted 40 million users, reflecting the huge interest in the social networking site which was opened to the public on September 20. Earlier, the service was available only through invitation as part of trial runs.

Interestingly, rival Facebook Inc took three years to reach the 25 million users mark and crossed the over 50 million active users mark in October, 2007. Facebook, founded in 2004, has now more than 800 million users across the globe.

"Google Plus is now open to everyone and we just passed the 40 million user mark. People are flocking into Google Plus at an incredible rate and we are just getting started," Google Chief Executive Larry Page said while announcing the company's latest quarterly earnings.

Google unveiled 'Google Plus' in late June as part of efforts to garner a share of the lucrative social networking space that has so far been dominated by Mark Zuckerberg-led Facebook.

During the quarter, Google has reported a 26 per cent jump in its net income to USD 2.73 billion in July-September 2011, helped by robust advertising business.

It registered revenue of USD 9.72 billion for the quarter ended September 30, 2011, an increase of 33 per cent over USD 7.28 billion in the same period last year.