The issue had also affected the company’s online messaging services Whatsapp and Messenger, with #whatsappoutage trending on Twitter in many countries, including India.
A Facebook spokesperson said the company had resolved the issue, which prevented access to its services.
Over one million people had reported problems with Instagram, while nearly 20,000 users posted about issues with WhatsApp, according to outage tracking website Downdetector.com.
Downdetector tracks outages by collating status reports from a series of sources, including user-submitted errors on its platform. The outages might be affecting a larger number of users.