Shafaq News / Amnesty International announced in a new toll that at least 304 Iranians were killed in the campaign launched by the Iranian authorities to suppress the protests that erupted after the three-day fuel price hike.
The human rights group had estimated the number of dead earlier at 208. Iran rejected these figures, describing them as "absolute lies."
Amnesty said that it had collected "horrific testimonies" indicating that after the authorities committed a "massacre" against the protesters, it had organized a "large-scale campaign" to cover the death toll.
"The Iranian authorities are launching a fierce campaign in the wake of the outbreak of nationwide protests on November 15," the London-based human rights supervisory body said in a statement.
It noted that "thousands of protesters were arrested in addition to journalists, human rights defenders and students to prevent them from speaking publicly about the harsh Iranian repression."
Demonstrations erupted across Iran after the shocking decision to raise fuel prices.
The authorities were able to regain control and impose order within days, but so far only five people have been killed, including four members of the security forces.
An official death toll is expected from the National Institute of Forensic Medicine in Iran.
"Independent sources" told Amnesty International that after a month of unrest, "security forces are still conducting raids across the country to arrest people from their homes and workplaces."
The organization revealed that adolescents as young as 15 have been "detained alongside adults".
With dozens in "solitary confinement" and others in "conditions amounting to enforced disappearance," some detention centers face a situation of "severe overcrowding," according to Amnesty International.
The organization called on Tehran to "urgently and unconditionally release all arbitrarily detainees."
The organization called on the international community to urgently put pressure on Iran, without which "thousands will remain at risk of torture and other forms of ill-treatment."