This morning, users have been reporting that the AppStore and all its derivatives (MacStore, iTunes Store) are currently down.
It is currently unknown what the cause of the service interruption is, and there is no current ETA on when it will be back up, but it seems to have started in the early hours of the morning (before 4AM).
Thanks to GeeksCorner for the update and information. You can view the current status of the Apple Services here.

By kito0920