According to Apple's System Status page, several of its services are experiencing downtime. Some users may be unable to access the iTunes Store, App Store, Mac App Store, and iBooks Store.
The page also suggests some users may be experiencing issues with the Apple TV, iTunes Match, iTunes Radio, iTunes U, and OS X Software Updates.
The downtime appears to have started just after 3pm and is ongoing. We have received several emails and tweets from users who are unable to access the App Store or can only access certain parts of the App Store.
iOS App Store Top Charts, for example, have been unavailable since the downtime originally began, and while some app categories were also blank, those seem to be reappearing, suggesting the outage may be short.
Today's App Store outage is the second Apple has seen this week.
Update: Apple's System Status page is back to normal, suggesting all issues have been fixed.