Iran is expected to block the popular messaging app Telegram, following similar measures taken by Russia, after the country’s supreme leader, Ayatollah Ali Khamenei, announced he was leaving the service to safeguard the national interest.

Telegram has proved a massive success in Iran, dwarfing the number of people using its global rival WhatsApp, and surpassing Facebook and Twitter, which have both been blocked for a long time in the country.

About 40 million Iranians – almost half of the country’s population – are estimated to be on Telegram, which has also appealed to older generations previously unfamiliar with the use of such social media platforms. In addition to one-to-one or group messaging, it allows users to broadcast posts to large audiences with its channel function.

Khamenei’s office announced on Wednesday that it was shutting down the ayatollah’s Telegram channel in order to safeguard national interests and end what it said was Telegram’s monopoly on the country’s social media.

The announcement also signalled that a nationwide ban on the app was imminent. “This move comes ahead of plans by the authorities to block Telegram and is aimed at supporting domestic social media apps,” read the brief message.

Iran’s vice-president, Eshaq Jahangiri, also announced that he was quitting Telegram. Officials also sent a directive to all civil servants and government departments telling them to stop using Telegram.

Iran has been mulling a ban on Telegram ever since protests over economic grievances at the end of last year took on a political dimension before spreading to up to 80 cities in January. Officials blamed Telegram for providing a platform for protesters to organise rallies.

The country’s technology minister personally reached out to Telegram’s founder, Pavel Durov, at the time, asking him to block channels that he alleged were spreading violence, prompting one such channel – that had been spreading misinformation – to be blocked.

Although officials have been entertaining the idea of a ban in recent months, the app’s popularity means they are wary of any public backlash. Telegram has also become a source of income for hundreds of Iranians behind popular channels.

A 23-year-old Iranian behind two cultural channels with over 80,000 followers said he was worried because he earned about £800 per month from posting ads. “I relied on it as a source of income, now I have to go and find another job. It wasn’t solely for entertainment, it was also my business,” said the Iranian user, who wished to remain anonymous.

“I built my channels during four years and filtering Telegram will put all that time and energy to waste.”

Iranians have shown huge resilience when it comes to the state blocking their access to online services, sites and social platforms. They have mastered anti-filtering software to bypass state restrictions and often migrate in their millions to a new platform when one is blocked. The success of Telegram is partly thanks to Iranians rapidly switching to the messaging service when Viber was blocked.

Earlier this month, Khamenei said it was religiously forbidden for officials to intrude upon people’s privacy through domestic apps, but that has done little to soothe concerns by ordinary people about domestic substitutes, particularly in a country where online censorship is rife and intelligence authorities resort to hacking without any judicial permission.

Iran’s moderate president, Hassan Rouhani, has strongly advocated free access to social media and messaging apps since coming to power in 2013. But the body that polices the internet in Iran is not under his full control, leaning more towards the ayatollah.

The news in Iran comes after Russia’s internet watchdog blocked an estimated 16m IP addresses in a massive operation against the banned Telegram messaging app four days after a court ordered the service to be blocked over alleged terrorism concerns.

On Tuesday, Edward Snowden, the NSA whistleblower living in Russia, came out in support of Durov, on Tuesday, tweeting: