WhatsApp, a popular messaging service owned by Facebook Inc, started to work again late Thursday after suffering a widespread global outage.

The reason for the problem remains unknown.

Many users took to Twitter to express their outrage as the app has become number one trend on Twitter within less than an hour with more than 280 thousands of tweets.

Service outages are common for rapidly growing technology companies as no statement from the company has been released so far.

WhatsApp's is used by more than 1.2 billion people around the world and is a key tool for communications and commerce in many countries. The service was acquired by Facebook in 2014 for $19 billion.