Instagram has gone down for some users across several cities, including London, San Francisco and Singapore.
Users took to Twitter to complain about the outage and tweeted messages along with the #instagramdown hashtag.
According to a check by Reuters, the app displayed an error message saying "couldn't refresh feed", while its website did not load for users.
Facebook and Instagram were not immediately available to comment.
DownDetector's live outage map showed that parts of North America, Europe, Australia, India, Singapore and other countries were facing issues with the service.
The global outage comes after Instagram announced on Monday that long-term insider Adam Mosseri will take over as the new head of the photo-sharing app, a week after its co-founders resigned.
The app has more than one billion active monthly users and has grown by adding features such as messaging and short videos.