Facebook's WhatsApp messaging service has resumed in Brazil after an appeals court overturned a suspension and many of the application's 100 million users in the country voiced outrage.
WhatsApp was cut off in Brazil at 2pm local time on Monday after a judge in the remote northeastern state of Sergipe ordered Brazil's five main wireless operators to block access to the app for 72 hours. The reason for the order was not made public, and it was the second such freeze in five months.
The suspension was lifted after about 24 hours when an appeals judge on Tuesday ruled in favour of an injunction by WhatsApp's lawyers, the court said in a statement.
The suspension highlighted growing international tensions between technology companies' privacy concerns and national authorities' efforts to use social media to gain information on possible criminal activities.
The same judge in Sergipe ordered the imprisonment of a Brazil-based Facebook executive in March in a dispute over demands to access the company's encrypted messaging service as part of a drug trafficking investigation.
Facebook chief executive Mark Zuckerberg called on Brazilians to demand his company's WhatsApp messaging service never be blocked again.
In a post in English on his Facebook page, the US billionaire and Facebook founder urged Brazilians to gather outside congress in the capital Brasilia at 6pm local time on Wednesday to rally in favour of legislation that would prevent internet services from being blocked.
"You and your friends can help make sure this never happens again, and I hope you get involved," Zuckerberg wrote on Facebook. He also posted a link to a petition, calling efforts to block communication "very scary in a democracy".
California-based WhatsApp had said in a statement on Monday that it was "disappointed" at the judge's decision to suspend its services. It said it had done the utmost to co-operate with Brazilian tribunals, but it did not possess the information the court was requesting.
Matt Steinfeld, a Facebook spokesman, said WhatsApp executives were meeting this week with law enforcement and judicial officials in Brazil to improve communication and clarify that the company cannot see users' encrypted messages and does not store them after transmission.
A Sao Paulo state judge ordered text message and internet voice telephone service for smartphones be shut down for 48 hours on December 15, after Facebook failed to comply with an order, although another court interrupted that suspension shortly afterward.
Monday's suspension angered many in Brazil, where more than 90 per cent of Android devices have WhatsApp installed.
Cost-conscious Brazilians are avid users of free messaging apps, and WhatsApp is by far the most popular.
The service is used by individuals, companies and federal and local governments to send messages and share pictures and videos.
