A Brazilian judge has ordered mobile-phone carriers to block access to WhatsApp for 72 hours throughout the country, the second such move against the messaging application in five months.
Monday's decision affects WhatsApp's 100 million-plus users in the country. The reason for the order is not known due to legal secrecy in an ongoing case in the court.
It is the second time since mid-December that WhatsApp has been the target of a blocking order.
The service was shut down for 48 hours on December 15 last year after Facebook failed to comply with an order, although another court interrupted that suspension shortly afterwards.
Judge Marcel Maia Montalvao of Sergipe state is the same judge who in March ordered the imprisonment of a Brazil-based Facebook executive for failing to comply with an attempted block on WhatsApp.
He was jailed and subsequently freed.
Twitter user Acaua Tavares reacted with the Portuguese acronym "PQP", roughly equivalent to "WTF?" in English, an agency reported.
"WhatsApp blocked again, PQP! That's Brazil," he wrote.
Many commenters reacted with a single question: "Again?"
Officials blamed the company for continuously failing to share information on WhatsApp users for an investigation into drug trafficking and organised crime.
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Mark Zuckerberg, the Facebook chief executive, was "stunned" by the "extreme decision".
In a statement, WhatsApp said the company was "disappointed at the decision" after doing the utmost to cooperate with Brazilian tribunals.
In 2013, Google too found itself under fire. The search engine giant's top Brazil executive was accused of breaking election laws when he refused to remove YouTube videos that were critical of a mayoral candidate in Mato Grosso do Sul state.
Reported non-cooperation from media companies is not that uncommon.
Last year, Apple refused to cooperate with the FBI in unlocking an iPhone used by one of the shooters in a mass killing by a couple in San Bernardino, California.