Instagram is back up after suffering a partial outage for over several hours, the photo-sharing social network platform said in a tweet.
But its parent Facebook's app still seemed to be down for some users across the globe.
Certain users around the world were facing trouble in accessing widely used Instagram, Whatsapp and Facebook apps yesterday, in one of the longest outages faced by the company in the recent past.
Social media users in parts of USs, Japan and some parts of Europe were affected by the outage, according to DownDetector's live outage map.
Facebook users, including brand marketers, expressed their outrage on Twitter with the #facebookdown hashtag.
The California-based company, which gets a vast majority of its revenue from advertising, told Bloomberg that it was still investigating the overall impact "including the possibility of refunds for advertisers."
A Facebook spokesman confirmed the partial outage, but did not provide an update.
The social networking site is having issues for over 12 hours, according to its developer's page.
Facebook took to Twitter to inform users that it was working to resolve the issue as soon as possible and confirmed that the matter was not related to a distributed denial of service (DDoS) attack.
In a DDoS attack, hackers use computer networks they control to send such a large number of requests for information from websites that servers that host them can no longer handle the traffic and the sites become unreachable.