Facebook has been inaccessible to some users around the world on Sunday, according to Downdetector, a website that monitors outages.
The site showed there had been more than 9,000 reports of problems accessing Facebook. Its live outage map showed the issues had mainly cropped up in Europe.
Downdetector also showed there were issues with WhatsApp and Instagram, which are owned by Facebook.
Facebook experienced one of its longest outages in March when some users had trouble accessing the site for more than 24 hours.