Indonesia on Friday blocked access to the encrypted messaging service Telegram, citing concerns that it was being used to spread "radical and terrorist propaganda" in the world's largest Muslim-majority nation.
The move comes amid heightened concerns over the growing presence and influence of Islamic State in Southeast Asia as the jihadist group loses territory in Syria and Iraq.
Indonesia itself has seen a resurgence in home-grown militancy, inspired in large part by Islamic State; a twin suicide bombing at a Jakarta bus station in May killed three police officers and injured several others. It has stepped up anti-terrorism cooperation with Malaysia and the Philippines.
"This has to be done because there are many channels on this service that are full of radical and terrorist propaganda, hatred, ways to make bombs, how to carry out attacks, disturbing images, which are all in conflict with Indonesian law," the communications ministry said in a statement on its website.
Telegram is a messaging platform known to be popular among Islamic State sympathizers, who use chatrooms with hundreds of members as well as private conversations.
The communications ministry added that both the mobile application and the desktop version of Telegram would be blocked throughout Indonesia. It did not say if it would take similar action against other messaging platforms.
Telegram was not immediately available for comment.
Many messaging apps such as Whatsapp and Telegram offer end-to-end encryption from sender to recipient, which means not even the companies providing the platform can see the messages.
Security officials in several countries have complained that the apps provide a safe space for militants to communicate with each other. Several governments, including those of Australia and Britain, have urged technology companies to do more to help security agencies thwart security threats.
In March, an attacker on London's Westminster Bridge was reported to have sent encrypted messages moments before plowing his car into pedestrians, killing four people, and fatally stabbing a police officer.
British interior minister Amber Rudd said at the time that such encryption was "unacceptable".