Social media platforms Facebook and Instagram, as well as messaging service WhatsApp, were unreachable on Sunday for more than three hours, users said.
The website Down Detector reported that thousands of people globally had criticized about the Facebook-owned trio being down from 11.30 BST onwards.
Facebook users were offered with the message: “Something went wrong.”
At 14:50, the site said it had fixed the issue after some users “experienced trouble connecting” to the apps.
Facebook did not comment on the reason of the problem, or say how many users had been affected.