PARIS - Several Iranians were on Sunday at risk of imminent execution over protests that have rocked the country's clerical regime, rights groups warned, after an international backlash over Iran's first hanging linked to the movement.

The almost three-month protest movement was sparked by the death of Mahsa Amini, who had been arrested by the Islamic republic's morality police.

It is posing the biggest challenge to the regime since the shah's ousting in 1979.

Iran calls the protests 'riots' and says they have been encouraged by its foreign foes.

Authorities are responding with a crackdown activists say aims to instill fear in the public.

Iran on Thursday executed Mohsen Shekari, 23, who had been convicted of attacking a member of the security forces. Rights groups said his legal process, which they described as a show trial, was marked by undue haste.

Iran's judiciary has reported that 11 people received death sentences so far in connection with the protests, but campaigners say around a dozen others are facing charges that could see them also receive the death penalty.

Unless foreign governments 'significantly increase' the diplomatic and economic costs to Iran, the world 'is sending a green light to this carnage,' said Hadi Ghaemi, executive director of the New York-based Center for Human Rights in Iran (CHRI).

Amnesty International said Iran was now 'preparing to execute' Mahan Sadrat, 22, just a month after his 'grossly unfair' trial. He was convicted of drawing a knife in the protests, accusations he strongly denied in court.

On Saturday, Sadrat was transferred from Greater Tehran Prison to Rajai Shahr prison in the nearby city of Karaj, 'sparking concerns that his execution may be carried out imminently,' Amnesty said.

'Show trial'

'Like all other death row prisoners, he was denied any access to his lawyer during the interrogations, proceedings and show trial,' said another group, Oslo-based Iran Human Rights.

Amnesty warned the life of another young man arrested over the protests, Sahand Nourmohammadzadeh, was also at risk 'after a fast-tracked proceeding which did not resemble a trial.'

He was sentenced to death in November on accusations of 'tearing down highway railings and setting fire to rubbish cans and tires,' the group said.

Among others given the same sentence is rapper Saman Seyedi, 24, from Iran's Kurdish minority. His mother pleaded for his life on social media in a video where she stated 'my son is an artist, not a rioter.'

Another dissident rapper, Toomaj Salehi, who expressed support for anti-regime protests, is charged with 'corruption on earth' and could face a death sentence, Iranian judicial authorities confirmed last month.

'We fear for the life of Iranian artists who have been indicted on charges carrying the death penalty,' United Nations experts said in a statement, referring to the cases of Sayedi and Salehi.

Amnesty and IHR have also raised the case of Hamid Gharehasanlou, a medical doctor sentenced to death. They say he was tortured in custody and his wife was coerced into giving evidence against him which she later sought to retract.

'Boundless contempt'

'Protester executions can only be prevented by raising their political cost for the Islamic Republic,' IHR director Mahmood Amiry-Moghaddam said, calling for a 'stronger than ever' international response.

The U.S., European Union members and the U.K. strongly condemned the execution of Shekari. German Foreign Minister Annalena Baerbock said it showed a 'boundless contempt for human life.'

Iran on Saturday and Friday again summoned the British and German ambassadors to protest their countries' actions, marking the 15th time in less than three months Tehran has called in foreign envoys as the demonstrations continue.

Many activists want the foreign response to go further, extending even to severing diplomatic ties with Iran and expelling Tehran's envoys from European capitals.

After the widespread international outrage at Shekari's execution, Iran said it was exercising restraint, both in the response by security forces, and the 'proportionality' of the judicial process.

Iran's use of the death penalty is part of a crackdown that IHR says has left at least 458 people killed by the security forces.

According to the U.N., at least 14,000 have been arrested.