PARIS, France (AFP) —Iran on Wednesday vowed fast-track trials for people arrested over a massive wave of protests, after United States (US) President Donald Trump threatened “very strong action” if the Islamic republic goes ahead with hangings.

International outrage has built over a crackdown on the demonstrations, which a rights group said has likely killed thousands in one of the biggest challenges yet to Iran’s clerical leadership.

Iranian authorities have insisted they have regained control of the country after successive nights of mass protests, repeatedly accusing the demonstrators of carrying out “acts of terror” of the kind committed by Islamic State.

Judiciary chief Gholamhossein Mohseni Ejei said on a visit to a prison holding protest detainees that “if a person burned someone, beheaded someone and set them on fire then we must do our work quickly,” in comments broadcast by state television.

Iranian news agencies also quoted him as saying the trials should be held in public and said he had spent five hours in a prison in Tehran to examine the cases.

Trump on Tuesday said in a CBS News interview that the US would act if Iran began hanging protesters.

“We will take very strong action if they do such a thing,” said the American leader, who has repeatedly threatened Iran with military intervention.

“When they start killing thousands of people — and now you’re telling me about hanging. We’ll see how that’s going to work out for them,” Trump said.

Tehran called the American warnings a “pretext for military intervention.”

Iran’s United Nations mission posted a statement on X, vowing that Washington’s “playbook” would “fail again.”

“US fantasies and policy toward Iran are rooted in regime change, with sanctions, threats, engineered unrest, and chaos serving as the modus operandi to manufacture a pretext for military intervention,” the post said.

Rights groups accuse the government of fatally shooting protesters and masking the scale of the crackdown with an internet blackout imposed on 8 January.

“Metrics show #Iran remains offline as the country wakes to another day of digital darkness,” said internet monitor Netblocks on Wednesday in a post on X, adding that the blackout had lasted 132 hours.

Some information has trickled out of Iran however. New videos on social media, with locations verified by AFP, showed bodies lined up in the Kahrizak morgue just south of the Iranian capital, with the corpses wrapped in black bags and distraught relatives searching for loved ones.

Tehran prosecutors have said Iranian authorities would press capital charges of “waging war against God” on some detainees.