Instagram, Facebook and Threads are experiencing widespread problems, locking users out of their accounts and failing to load properly.
Outages reported on Down Detector shot up just before 3pm, with more than 300,000 problems logged.
More than 25,000 Instagram outages were also reported via the website, which collates status reports from several sources, including users.
Problems on Facebook appear to leave users unable to login, with users logged out and unable to reset their password or access their accounts.
On Instagram, there are problems loading users' timelines, stories and comments.
Sky News has contacted Meta, the parent company for both platforms, for comment.
Sky News understands some of Meta's internal systems have also been affected by the outage.
WhatsApp, which is also owned by Meta, does not appear to be impacted by the problems.
Andy Stone, communications director at Meta, posted on X, formerly Twitter:
"We're aware people are having trouble accessing our services. We are working on this now."
(c) Sky News 2024: Instagram and Facebook down for tens of thousands of users
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