HRW slams Iran's banning of Telegram as 'unjustifiable'
"The Iranian judiciary's blocking of the messaging application Telegram is an unjustifiable restriction on freedom of expression and access to information," the US-based rights organisation said in a statement.
Human Rights Watch accused Tehran of "stifling access to information to try to make its problems go away" and said such censorship "should never be used to protect leaders from scrutiny".
On Monday, a Tehran judge blocked Telegram following accusations that the hugely popular app has allowed armed opposition groups to fuel unrest.
The decision was described as "just another stain on Iranian authorities' already dismal record on freedom of expression" by Human Rights Watch.
Telegram is the Islamic republic's most popular social network with some 40 million users, around half the population.
The move to ban the app has highlighted differences of opinion between the government of reformist President Hassan Rouhani and ultra-conservatives who control the judiciary and security services.
Reflecting the government's support of more open access to the internet, telecoms minister Mohammad Javad Azari Jahromi on Tuesday highlighted problems in Russia since authorities there banned Telegram.
"These problems could happen in Iran as well," he said, quoted by the ISNA news agency, after thousands rallied in Moscow on Monday in support of internet freedom.
During a wave of protests that hit dozens of Iranian cities at the start of the year, authorities temporarily banned Telegram, saying the service enabled foreign-based "counter-revolutionary" groups to stir tensions.
Since then, authorities have sought to develop Iranian social media networks and limit the reliance on foreign-based platforms, which Tehran accuses of hosting sites deemed hostile to the Islamic Republic.
Several Iranian platforms offering services similar to Telegram have emerged in recent months, like the Soroush network, which already claims to have five million subscribers.
Iran's supreme leader Ayatollah Ali Khamenei and President Hassan Rouhani both announced in mid-April they would stop using Telegram.
The last message on Khamenei's Telegram channel directed users to accounts on Iranian messaging services, including Soroush and Gap.