Google said Thursday its social network had grown to 135 million active users, and added a photo-sharing app similar to Facebook's Instagram.

"Today Google+ is the fastest-growing network thingy ever," said Google senior vice president Vic Gundotra in a blog post. "More than 500 million people have upgraded, 235 million are active across Google (+1'ing apps in Google Play, hanging out in Gmail, connecting with friends in Search...), and 135 million are active in just the stream," he added.

Google also introduced the mobile photo-sharing service Snapseed, to the social network. The service allows users to crop and enhance pictures before posting to social networks.

Snapseed is rolling out now to Google Play and the App Store, and starting today, both versions are free.

Google+ will be also adding a new feature called "Communities" which makes the Google+ "hangouts" permanent locations.

"Google+ has always been a place to crowd around common interests and meet new people. What's been missing, however, are more permanent homes for all the stuff you love: the wonderful, the weird, and yes, even the things that are way out there. With Google+ Communities there's now a gathering place for your passions."