Iran carried out its first known execution Thursday over the protests that have shaken the regime since September, hanging a 23-year-old man after a legal process denounced as a show trial by rights groups.
Mohsen Shekari was convicted and sentenced to death for blocking a street and wounding a paramilitary during the early phase of the protests in mid-September.
At least a dozen other people are currently at risk of imminent execution after being sentenced to hang over the protests in recent weeks, human rights groups warned.
Demonstrations have swept Iran for nearly three months since Mahsa Amini, 22, died after her arrest by the morality police in Tehran for an alleged breach of the country's strict hijab dress code for women.
The protests, described by the authorities as "riots", are posing the biggest challenge to the Islamic republic since it was established following the ouster of the shah in 1979.
"Mohsen Shekari, a rioter who blocked Sattar Khan Street in Tehran on September 25 and wounded one of the security guards with a machete, was executed this morning," the judiciary's Mizan Online website said.
Mahmood Amiry-Moghaddam, director of Oslo-based group Iran Human Rights (IHR), urged a strong international reaction "otherwise we will be facing daily executions of protesters."
He said Shekari had been "sentenced to death in show trials without any due process".
"This execution must have rapid practical consequences internationally," he tweeted.
Iranian dissident Hossein Ronaghi, recently released after a spell in jail, warned the authorities: "The execution of any protester will have serious consequences for you.
"Taking the life of one person is taking all of our lives. Do you have enough gallows?" he asked on Twitter.
- 'Inhumane' -
In one of the first international reactions, Austria's foreign ministry said the execution was "disproportional and inhumane", urging the government to "stop all further executions" related to the protests.
The revolutionary court in Tehran heard Shekari had been arrested after striking the member of the Basij paramilitary force in the shoulder with the blade, an injury that required 13 stitches, Mizan Online said.
The judiciary said Shekari was found guilty of fighting and drawing a weapon "with the intention of killing, causing terror and disturbing the order and security of society".
It convicted him of "moharebeh" -- or waging "war against God" under Iran's Islamic sharia law -- on November 1, said Mizan, adding that he appealed the ruling but the supreme court upheld it on November 20.
Iran executes more people annually than any nation other than China. IHR said earlier this week it had already executed over 500 people this year, a sharp jump on last year's figure.
The largely peaceful protest movement has been marked by actions included removing and burning headscarves in the streets, chanting anti-government slogans and confronting the security forces.
In a relatively new tactic, protest supporters staged three days of nationwide strikes up to Wednesday which closed down shops in several major cities including Tehran, according to rights groups.
- 'Imminent danger' -
The security forces have responded with a crackdown that has killed at least 458 people, including 63 children, according to an updated death toll issued by IHR on Wednesday.
The crackdown, which has drawn widespread international criticism, has seen thousands of people arrested, including academics, journalists and lawyers.
The United Nations Human Rights Council on November 24 voted to create a high-level investigation into the crackdown.
An Iranian court on Tuesday sentenced five people to death by hanging for killing a Basij member, a ruling condemned by human rights activists as a means to spread fear and to stop the protests.
The judgement brought to 11 the number of people in Iran sentenced to death in connection with the protests, in what Amnesty International said was a strategy using the death penalty as a "tool of political repression to instil fear".
Freedom of expression group Article 19 said urgent action was needed "as the lives of others on death row in relation to the uprising are in imminent danger".
"It is deeply shocking and beyond the pale of justice and due process that 23-year-old Mohsen Shekari was executed this morning after a swift and sham trial," it added.
In a tweet, former Iranian football star Ali Karimi, a strong supporter of the protests, warned: "If we stay silent today, tomorrow we will be using the 'Do not execute' hashtag for other children of Iran."
Prior to the latest execution, Amnesty had said at least 28 people, including three children, could face the death penalty in connection with the nationwide protests.