Human Rights Watchdog Amnesty International said Iran has been using torture to extract confessions from hundreds of people who have been jailed since a brutal crackdown against protests last year.
Nation-wide demonstrations erupted in Iran in November 2019 after a significant petrol price rise. The Iranian security forces brutally put down the protests with mass arrests amid a total internet blackout.
A report by Reuters claimed that Iranian security forces killed at least 1500 people on the streets.
Amnesty announced that it had gathered dozens of testimonies from the 7,000 people who were arrested, which involved children as young as 10.
Video recordings, court documents and statements by the authorities were also evaluated, according to the agency.
The findings reveal "a catalogue of shocking human rights violations, including arbitrary detention, enforced disappearance, torture and other ill-treatment", Amnesty said.
Iranian officials remain silent about the incidents.
Amnesty added that those arrested were tortured into "confessions" of involvement in the protests, membership of opposition groups or contact with foreign governments and media.
The rights group also said it recorded the names of more than 500 people "subjected to unfair criminal proceedings".
Torture techniques listed as waterboarding, beating, electric shocks, pepper-spraying genitals, sexual violence, mock executions and pulling out finger and toe nails, Amnesty reported.
"It felt like my entire body was being pierced with millions of needles," one man allegedly tortured with electricity told Amnesty.
Another man said he was suspended from his hands and feet from a pole - a method reportedly called "chicken kebab" by his interrogators - the report read.