Social networking features have been added to Gmail with Buzz. Picture: Google. Source: news.com.au

Google Buzz product manager Todd Jackson equated the enhanced offering to "an entirely new world in Gmail" during an unveiling presentation at the internet giant's headquarters in Mountain View, California.

Buzz began rolling out today with Google web-based email service getting updates about what friends are doing online and ways to share video, photos and other digitised snippets with others of one's choosing.

Google's move comes as a direct challenge to social-networking stars Facebook and Twitter, which thrive on enabling people to share experiences, activities and thoughts as they go through their days.

As is the case with wildly popular microblogging service Twitter, Buzz lets users "follow" people that share updates with the world.

Yahoo! added a similar feature to its email program, Yahoo Mail, last year, allowing users to see whether friends have uploaded a photo to a photo-sharing site such as Flickr.

In what could signal an escalating battle between Google and Facebook, the leading social-networking service celebrated its sixth birthday last week with changes that included a new message inbox that echoes the Gmail format.

Facebook boasts some 400 million users while Gmail had 176 million unique visitors in December, according to tracking firm comScore.