The campaign is a blow to President Masoud Pezeshkian, whose election in 2024 owed much to reformist support.

He had expressed a more conciliatory view of the protesters, but appears to have been largely sidelined.

Pezeshkian has also called for an inquiry into the protests, but the weakness of both his personal position and that of the presidency itself within the Iranian theocratic system appears to have been exposed once again.

The crackdown on the prominent reformists sends a signal that more moderate voices are being further silenced, just days after Iranian and US officials held talks on trying to reach a deal on Iran's nuclear programme.

Both sides have described the initial discussions in Oman as positive, although no concrete progress appears to have been made so far.

In another indication that hardliners in Iran are still calling the shots, the semi-official Tasnim news agency says that Ali Larijani - a close adviser to the Supreme Leader Ali Khamenei and secretary of Iran's Supreme National Security Council - is to head to Oman for talks with Omani mediators on Tuesday.

Negotiations with the Trump administration are said to be focusing on Iran's nuclear programme.

That's led protesters inside Iran and their supporters outside to bemoan an apparent change of approach by the US from its initial stance of vowing a decisive response if the regime killed people participating in the demonstrations.

The huge build-up of US military forces in the region remains in place, with its threat of an all-out attack on Iran.

The Iranian regime is hoping to avert this through negotiations and possible concessions.

But this latest move against what's left of the opposition is likely to make building any sense of trust with Washington more elusive.