The US has demanded that the “brutal” leadership of Iran release all those arrested during recent anti-government protests.
A White House statement said the Trump administration was “deeply concerned” that Iran had imprisoned thousands for engaging in “peaceful protests”.
It is not known how many people have been arrested.
The official figure is about 1,000, but other sources in Iran suggest it could be much higher.
Iranian officials say the majority of those arrested have now been released, with only “instigators” facing trial.
The unrest – the largest of its kind since a disputed presidential election in 2009 – initially began over price rises and corruption.
But it quickly spiralled into a wider display of animosity towards the government and ruling clerics. At least 21 people were killed in violence between protesters and the authorities.
The latest US support for the protesters comes as President Donald Trump is deciding whether to continue to extend Iran’s relief from sanctions before a deadline on Friday.
The relief is in return for Iranian compliance with a 2015 deal on curbing its nuclear activity.
The White House statement, issued in the name of press secretary Sarah Sanders, said: “The Trump administration is deeply concerned by reports that the Iranian regime has imprisoned thousands of Iranian citizens in the past week for engaging in peaceful protests.
“Further reports that the regime has tortured or killed some of these demonstrators while in detention are even more disturbing.
“We will not remain silent as the Iranian dictatorship represses the basic rights of its citizens and will hold Iran’s leaders accountable for any violations.”
The statement went on to demand the immediate release of all political prisoners in Iran.
Source » bbc