The game uses GPS to track a player's location and overlays "monsters" that can be hunted in that location on his mobile screen. The captured monsters can then be trained for battles.
While on a daily basis, it is being used twice as much as the Facebook app on Android, the popular app from Niantic Labs has the most first-week downloads since Apple launched its iOS app store eight years ago.
During its first week, Pokemon GO users spent 75 minutes per day playing, versus only 35 minutes on the Facebook app, media reported.
The augmented reality game has also become the most downloaded mobile app in its first week of release in the history of the app store.