Iranian MPs have criticised the arrests of journalists and social media organisers ahead of the presidential election in May, with one directly accusing the elite Revolutionary Guards in a letter published Saturday.
The arrests in recent days are alleged to have targeted unnamed people who run channels on the popular messaging site Telegram supporting reformists and the moderate government of President Hassan Rouhani.
Two prominent journalists -- Ehsan Mazandarani and Morad Saghafi -- have also been detained.
Mahmoud Sadeghi, a reformist MP, wrote an open letter to Revolutionary Guards commander Mohammad-Ali Jafari, calling on the organisation to stay out of politics.
"Some incidents in recent days, including the simultaneous arrests of managers of Telegram channels with close associations to reformists and supporters of the government, which has apparently been done by the intelligence arm of the Sepah (Revolutionary Guards), has raised a wave of concern in society," Sadeghi wrote in the letter published by the ILNA news agency.
Several other MPs have also criticised the arrests in open letters this week.
Outspoken moderate-conservative MP Ali Motahari threatened to seek the impeachment of the intelligence minister if he did not provide details of the arrests.
The Revolutionary Guards operate their own intelligence wing independently of the government and answerable only to supreme leader Ayatollah Ali Khamenei.
Rouhani, who will seek re-election on May 19, has united moderates and reformists with his efforts to improve relations with the West, despite largely failing to win the release of jailed opposition leaders or improve civil rights as he promised during the 2013 campaign.
Telegram, which has an estimated 20 million users in Iran, has become the leading site for political and cultural discussions in a country where Facebook and Twitter are banned.
The authorities have tried to control the site, demanding that channels with more than 5,000 followers register with the government.
A reformist newspaper also reported Saturday that Faezeh Hashemi, daughter of revolutionary founder Akbar Hashemi Rafsanjani, had again been sentenced to six months for "spreading falsehoods" after she accused the judiciary of corruption.
Hashemi, a vocal supporter of opposition leader Mir Hossein Mousavi during the mass protests that followed the disputed 2009 election, previously served six months in jail for "disrupting public opinion" in 2012-13.