Facebook Inc's main social media site, popular photo-sharing platform Instagram and messaging app WhatsApp, were down for tens of thousands of users, according to outage tracking website Downdetector.com.
Reuters could not immediately confirm the issue affecting the services. However, the error message on Facebook's webpage suggested a Domain Name System (DNS) error.
DNS allows web addresses to take users to their destinations. A similar outage at cloud company Akamai Technologies Inc took down multiple websites in July.
"We're aware that some people are having trouble accessing our apps and products," the social media giant's official Twitter handle said on Monday.
"We're working to get things back to normal as quickly as possible, and we apologize for any inconvenience." The official handles of WhatsApp and Instagram also took to Twitter to confirm the outage.
Facebook shares fell 5.5% in afternoon trading on Monday, inching towards its worst day in nearly a year.
Downdetector, which only tracks outages by collating status reports from a series of sources, including user-submitted errors on its platform, showed there were more than 50,000 incidents of people reporting issues with Facebook and Instagram. The outage might be affecting a larger number of users.
Meanwhile, the social-media giant's instant messaging platform WhatsApp was also down for over 35,000 users, while Messenger was down for nearly 9,800 users.
Facebook has experienced similar widespread outages with its suite of apps this year in March and July.
Several users using their Facebook credentials to log in to third-party apps such as Pokemon Go and Match Masters were also facing issues.
"If your game isn't running as usual please note that there's been an issue with Facebook login servers and the moment this gets fixed all will be back to normal," puzzle game app Match Masters said on its Twitter account.