The last time this happened in mid-March, Facebook blamed a "server configuration change" that resulted in an unprecedented, cascading series of issues persisting for over 24 hours.
However, Facebook did not specify the cause or scope of the outages.
Facebook, Instagram and WhatsApp users on Sunday experienced difficulties accessing the social network sites and messaging service.
A response from a Facebook representative reads, "Earlier today, some people may have experienced trouble connecting to the family of apps ..."
Downdetector.com's live outage map showed the issues mainly cropped up in Europe and Asia.
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The website wouldn't refresh, and messages weren't coming through, from roughly 6:30 AM EDT (New York time) to about 9:30 AM.
Facebook explained that they have resolved the issues and the systems are recovering after the problems.
Lesego Semenya said: "Seems Facebook, WhatsApp and Insta are all down".
Instagram, facebook and WhatsApp are down.
DownDetector.com, a website which tracks online service outages, lists tens of thousands of reports from users confirming the sites are down in their area.
Facebook will likely issue comments on the outage via its Twitter accounts, but it may be a while before those statements are published.