Apple's iMessage and Facetime messaging systems have been hit with a glitch that has taken the services offline for several hours.

The problems for both services began shortly after noon Pacific Time (7 p.m. GMT) Tuesday and continued at the time of this writing, more than four hours later.

IMessage is an instant messaging service and Facetime is a video calling service.

Apple posted a short notice on its website saying "some users" were unable to make calls or send messages but provided no additional information.

It was unclear how widespread is the outage, but Twitter is seeing tens of messages every minute from users who say they are affected by the problem.

Of the two services, Facetime is the older, having been introduced with the iPhone 4 in 2010. IMessage was introduced a year later when Apple released iOS 5.

This isn't the first time the servers have gone down. Read: 

Apple's iCloud broke yesterday, was everyone testing Apple's spam filter?

Apple confirms iCloud mail outage for some users

Apple's iMessage, FaceTime servers were down, now back online


iOS 7 release date, rumours and leaked images

Apple hiring to improve Maps, FaceTime, iMessage; Rare Steve Jobs photos from 1996; Google disqualifies Glass 'Explorers'

Security experts applaud Apple's new two-factor authentication

Apple updates Podcasts app, adds custom stations, playlists, iCloud sync, ditches tape deck design