Google Inc trotted out the latest improvements to its Google+ social network on Tuesday, integrating its search engine into the site and expanding its Hangouts feature to allow mobile use and broadcasting.

The tweaks underscored how the Internet search and advertising leader is ramping up its 3-month-old social network to take on Facebook and fight to attract and retain Web surfers' time online.

On Tuesday, the company said on its official blog that the well-received Hangouts feature -- where up to nine users can link up and chat on video -- will now be available on smartphones equipped with cameras and powered by its own Android software. Support for Apple Inc devices is coming soon, it added.

Hangouts should keep pace with how you socialize in the real-world, so today we're launching it on the one device that's always by your side: your mobile phone, senior vice president of engineering Vic Gundotra said on the blogpost.

Google did not say how many people had signed up so far, but confirmed the social network was now open to all, whereas previously it had been invitation-only. Analysts estimate upwards of 25 million users have joined Google+ since its inception.

The company also made its search engine available from within the social network. Users can search from Google+ and get results not just on the network, but from the worldwide Internet.

(Reporting by Edwin Chan; editing by Andre Grenon)