In a move underscoring the escalating battle among Internet companies over what is known as social media, Google Inc. (GOOG) on Monday launched a tool that allows users to find postings from their friends as part of a Web search.

Google Social Search, which is available starting Monday, includes relevant postings by colleagues, friends and selected media sources on feeds from Twitter Inc. and on blogs, as well as in broader Internet searches on its search engine. The Mountain View, Calif.-based company posted details of the new product on a blog.

A search for a restaurant could generate not only official sites and mainstream media reviews, but also comments from friends or colleagues on a range of different blogs or social sites, if they had set up a profile that allowed their data to be searched.

Social Search is being launched days after both Google and Microsoft Corp. (MSFT), Google's main rival in Internet search, announced separate deals with start-up micro-blogging site Twitter Inc. Microsoft also announced a similar deal with Facebook Inc. to get access to its user information. Microsoft owns approximately 1.6% of Facebook, following a 2007 investment.

San Francisco-based start-up Twitter, which lets users blast short messages from computers and mobile phones which are then displayed on their pages, has seen explosive growth until recently. Marketers are increasingly looking for ways to tap social media such as Twitter and Facebook for ways to better track trend-making topics and reach younger users.

It wasn't immediately clear how Social Search relates to the deal Google announced with Twitter. Google didn't immediately respond to a request for comment.

-By Jessica Hodgson, Dow Jones Newswires; 415-439-6455; jessica.hodgson@dowjones.com