Mobile phone companies in Brazil have been ordered by a court to impose a block of the popular WhatsApp smartphone applicationfor two days.
A court in Sao Paulo state made the order because it said WhatsApp had repeatedly failed to co-operate in a criminal investigation.
It is not clear if mobile companies will fully comply with the order.
Facebook owns the app. Its chief executive Mark Zuckerberg said he was "stunned" by the "extreme" ruling.
WhatsApp is reported to be the most used application in Brazil, with about 93 million users.
Local media said the order to suspend the services was related to a drug trafficking trial in Sao Paulo State.
The court tried to get access to a suspect's WhatsApp messages but the firm refused to share them, Folha newspaper reported.
The court says WhatsApp failed to comply with judicial orders in July and in August.
Judge Sandra Regina Nostre Marques finally ordered the 48-hour shut-down on Wednesday, after finding out that WhatsApp had persisted in ignoring its rulings.
She said the suspension order was being made under terms of the country's internet legislation.
The move against WhatsApp comes as Brazilian phone companies have urged the government to restrict the use of free voice-over-internet services offered through WhatsApp.
The phone companies argue that the rise of WhatsApp has damaged their businesses.
Meanwhile other messaging services say they are benefiting from the temporary absence of WhatsApp.
One such company, Telegram, said on Twitter that more than 1.5 million Brazilian users had joined up since the court order was handed down.