WhatsApp was hit by a major outage on Friday morning, preventing people around the globe from using the world's most popular messaging app.
Users of the Facebook-owned app could not send or receive messages as the service continued to say it was "connecting", though no connection was made.
According to DownDetector, there were problems across Europe although users in India, Pakistan, Singapore and Iraq also reported that they could not access the service.
Whatsappdown was the top trending item on Twitter in India, which is the app's largest market. Around 200 million of the messaging app's billion-plus users are based in India.
A spokesperson for Facebook in Singapore said the company was investigating the matter, Reuters reported.
The online messaging app went down in the U.K. at approximately 8:30 a.m. GMT (4.30 a.m. ET), before users were able to reconnect around 30 minutes later.
The reported connection error comes as Apple released the iPhone X on Friday, with people eagerly anticipating the tech giant's latest flagship phone in stores globally.
Facebook was not immediately available for comment when contacted by CNBC.