The security forces fired "live ammunition, metal pellets and teargas" at protesters when a group of people gathered for a protest outside a police station in Zahedan, says Amnesty International.
At least 82 people have been killed by Iranian security forces in the city of Zahedan in the southeastern Sistan-Baluchistan province since protests erupted there on September 30, Amnesty International said.
In a violent crackdown after Friday prayers on September 30, security forces killed at least 66 people, including children, Amnesty said on Thursday.
Since then, 16 people have been killed in an ongoing clampdown on protests, it added, warning the real toll is likely to be even higher.
With Iran already convulsed by protests over the death of Mahsa Amini who had been arrested by the Tehran police, the protests in Zahedan were triggered by anger over the reported rape of a teenage girl by a police commander in the region.
Amnesty said that security forces fired "live ammunition, metal pellets and teargas" at protesters, bystanders and worshippers when a group of people gathered for a protest outside a police station after Friday prayers on September 30 in Zahedan.
'Intent to kill or seriously harm'
"Evidence gathered by Amnesty International shows that the majority of victims were shot in the head, heart, neck and torso, revealing a clear intent to kill or seriously harm."
It added that the firing had come from the "police station rooftop".
At least three children were killed on September 30, it added.
Iranian officials have characterised the unrest as attacks by "extremists" on police stations that left five members of the Revolutionary Guard dead.
But Amnesty said that beyond "a minority" of protesters throwing stones towards the police station, it had found "no evidence" the conduct of protesters posed a serious threat to security forces.