The letter was reportedly sent to Afghan ISPs after the country's National Directorate for Security ordered the move, in what some observers believe is an attempt to prevent use of the encrypted messaging services by the Taliban and other insurgent groups.
According to Reuters, the letter by telecoms regulator ATRA, dated November 1 and signed by an official of the regulator, directed internet companies to block Telegram and Facebook's WhatsApp services "without delay" for a period of 20 days.
However, the temporary ban does not yet appear to have been enforced, with both services said to be still working normally on Saturday on both state-owned operator Salaam and private service providers.
Public use of mobile phones has boomed in Afghanistan since the Taliban was removed from power by a U.S-led campaign in 2001, while use of services like WhatsApp, Messenger, and Viber are popular among the country's politicians as well as the Taliban, which also maintains a sophisticated social media operation.
However, civil rights groups and Afghan social media users have criticized the attempt to block the chat platforms. Many argue such a ban is unenforceable anyway because it can be circumvented by the use of virtual private networks (VPNs).
Prominent newspaper editor Parwiz Kawa told the BBC that his country was finally an open society after years of censorship, therefore any ban on social media would not be tolerated.
"The public reaction - including our own front page - is to resist," he said. "We can't tolerate any ban on social media or any censorship."
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