Iran's supreme leader Ayatollah Ali Khamenei announced Wednesday that he would no longer use the hugely popular messaging app Telegram, shifting instead to domestic services.
The office of President Hassan Rouhani meanwhile issued a directive banning the government and administration workers from using foreign messenger apps to communicate, according to the official IRNA news agency.
The announcements came as rumours continued that Iran would soon block Telegram, built by Russian tech guru Pavel Durov and the most popular social media service in the country with some 40 million users -- roughly half the population.
"In line with safeguarding national interests and removing the monopoly of the Telegram messaging network, the website for the preservation and publication of the works of Grand Ayatollah Khamenei will stop its activities in this network from this moment," said the last message on Khamenei's Telegram channel.
It directed users to accounts on Iranian messaging services, including Soroush and Gap, which the authorities are trying to promote.
First Vice President Eshagh Jahangiri and foreign ministry spokesperson Bahram Ghassemi followed suit by closing their Telegram accounts on Wednesday, IRNA reported.
Last week, Khamenei issued a statement saying any breaches of online privacy were "haram", meaning they were religiously forbidden.
This was interpreted as seeking to encourage the use of domestic apps, which many Iranians fear will be monitored by intelligence services.
Khamenei's channel said his move away from Telegram was an initial step towards stopping its use by all "official bodies".
On Sunday, the ministry of education banned the use of foreign social media networks in schools.
During a wave of protests that hit dozens of Iranian cities in December and January, Iranian authorities temporarily banned Telegram, accusing it of allowing foreign-based "counter-revolutionary" groups to fuel unrest.
But the government of President Hassan Rouhani has pushed back against efforts to block Telegram and other popular services such as Instagram, saying thousands of businesses use the service and access to the outside world should not be curtailed.
On Tuesday conservative lawmaker Abolfazl Abutorabi said "all foreign messaging services" could be banned on April 21, with Telegram first to go.
Soroush claims to have some 5 million users, while Gap has more than 1.3 million.
There was no word on whether Khamenei's office would stop using his five Twitter feeds in different languages, which exist despite the service being blocked for ordinary Iranians.
Facebook and Twitter are both blocked in Iran, although they are easily accessible using virtual private network (VPN) software.