Facebook's mobile app has added a feature that will now allow users to discover and track down friends who live near them by using smartphone locations, Agence France-Presse reported.

The feature, called "nearby friends," is optional and "helps you discover which friends are nearby or on the go," said product manager Andrea Vaccari in a blog announcement.

"If you turn on Nearby Friends, you'll occasionally be notified when friends are nearby, so you can get in touch with them and meet up," Vaccari said.

"For example, when you're headed to the movies, Nearby Friends will let you know if friends are nearby so you can see the movie together or meet up afterward."

Following the footsteps of the network Foursquare, numerous dating apps and the recently launched social network aggregator SocialRadar, Facebook will be basing their model on these location-based service features, according to AFP.

"You can choose who can see if you're nearby (for example: your friends, close friends, or a specific friends list) and you can turn it on and off at any time," Vaccari said.

However, the sharing of the location is required to be mutual between the two parties.

"You and your friends both have to turn on Nearby Friends and choose to share with each other to see when you're nearby. Your friends will only be able to see that you're nearby if you share this info with them and vice versa."

A set period of time will also be allocated for the precise locations to be shared between users.

"When you share your precise location, the friend you choose will see exactly where you are on a map, which helps you find each other," said Vaccari.

While Facebook had an estimated 1.23 billion users at the end of December, the mobile device is used by more than one billion to browse the social network, AFP reported.

The "nearby friends" feature will be available for Android and iPhone users in the United States over the coming weeks.