Instagram has stopped working, with users unable to load the app.
The problems came at the same time as parent company Facebook is also being hit by technical issues. WhatsApp, the company's other major app, appeared to still be working.
People reported being unable to log in or to get into the app, being greeted instead by error messages.
"Error," one read. "We're sorry, but something went wrong. Please try again."
Facebook addressed the problems on its Twitter account.
"We’re aware that some people are currently having trouble accessing the Facebook family of apps," it wrote. "We’re working to resolve the issue as soon as possible."
Reports of the outages were largely focused in the UK, rest of Europe and the east coast of the US, according to outage tracking website Down Detector. But that might simply be because timezones mean much of the rest of the world is asleep.
The problems came on a busy day for outages, with the world having been hit by significant issues when trying to log in to Gmail and other Google sites earlier in the day.
Unlike Facebook, Instagram does not operate an official platform status page to give information about outages.
But the Facebook page claims there is no issue with the site, despite thousands of reports of issues.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies