Iranian state television aired a video on Saturday in which a champion wrestler facing two death sentences appeared to confess to killing a water company security guard during anti-government protests in 2018.
The case of wrestler Navid Afkari has caused an outcry from Iranians and human rights groups. U.S. President Donald Trump on Thursday called on Iran not to execute the 27-year-old Afkari.
Iran's Supreme Court has upheld the two death sentences against Afkari, who was convicted of stabbing to death the guard and other charges, according to state media.
The killing came during some of the worst unrest in the country in a decade after a rise in fuel prices. Iran's clerical rulers have blamed the street protests on "thugs" linked to exiles and foreign foes - the United States and Israel.
The television showed what appeared to be written confessions by Afkari, but he has said in a recording circulated on social media that he was coerced to sign the documents.
"I hit twice, once and then again," Afkari was shown saying with a stabbing gesture during a police reconstruction of the killing of the middle-aged victim, Hassan Turkman, a water company security guard.
Afkari's attorney said there was no clear evidence proving his client's guilt.
"There is no picture of the moment of the crime. The alleged video is from an hour before the murder," Hassan Younesi said on Twitter.
Iran's state media often air purported confessions by suspects in politically charged cases.
The International Federation for Human Rights and London-based Justice for Iran said in a report in June that Iranian state media have aired more than 355 forced confessions in the past decade. Iranian officials reject such accusations.