Google Inc injected social networking features into its popular Web email product as the world's No. 1 search engine seeks to fend off competition from Facebook and Twitter.

Google introduced a new product dubbed Google Buzz on Tuesday that allows users to quickly share messages, Web links and photos with friends and colleagues directly within Gmail, the company's popular email product.

And the company unveiled a handful of new products designed to make the new social networking features suited to mobile devices, like smartphones based on Google's Android operating system.

Google's new social networking technology mimics some of the key features of popular social networking services like Twitter and Facebook, which are increasingly challenging Google for web surfers' online time.

Gmail is the third most popular Web based email in the world, with 176.5 million unique visitors in December, according to comScore. Microsoft Corp's Windows Live Hotmail and Yahoo Inc's Mail were No. 1 and No. 2, with 369.2 million unique visitors and 303.7 million unique visitors respectively.

In addition to the Buzz features for Gmail, Google said it is launching a special mobile application for Buzz, as well as weaving Buzz technology into the mobile versions of its flagship Web site and its maps products.

Google has tried to ride the social networking wave before, launching the Orkut social network in 2004. But while Orkut is big in certain overseas markets, like Brazil, it has failed to attract as many users as social giants like Facebook and MySpace in the United States.

In building a social network on top of an email product, Google is following in the footsteps of Yahoo, which has taken a similar approach in efforts to keep up with Facebook.

(Additional reporting by Ian Sherr, editing by Gerald E. McCormick)