Iranian state TV has said security forces killed what it called "thugs and rioters" during last month's mass protests against a petrol price rise.
Iran has faced growing global criticism and pressure over the security force crackdown on demonstrations that spread across at least 100 cities and towns throughout the Islamic Republic in mid-November.
Altogether, from 180 to 450 people, and possibly more, were killed in four days of intense violence after the gasoline price increase was announced on November 15, with at least 2,000 wounded and 7,000 detained, according to global rights organizations, opposition groups and local journalists.
Iranian officials have disputed Amnesty's figures but have offered no definitive accounts of how many people have been arrested, injured or killed in the protests following the theocratic government's announcement that it would raise gas prices by 50 percent to fund handouts for the country's poor.
On Tuesday, Iranian television said those killed included rioters who had attacked sensitive or military centres with firearms or knives or who had taken hostages in some areas.
In another case, the report said security forces confronted a separatist group in the city of Mahshahr armed with "semi-heavy" weapons.
"It's something pretty unprecedented event in the history of the human rights violations in the Islamic Republic", Mansoureh Mills, an Iran researcher for Amnesty International, told AP.
"For hours, armed rioters had waged an armed struggle", the report alleged. The report said passersby, security forces and peaceful protesters were also killed, without assigning blame for their deaths.
"In addition to the selective portrayal of destruction of public property, (state-run) Islamic Republic of Iran Broadcasting should show a few protesters being shot", lawmaker Mahmoud Sadeghi of Tehran wrote sarcastically. "In such circumstances, security forces took action to save the lives of Mahshahr's people".
The oil-rich province's Arab population has long complained of discrimination by Iran's central government and insurgent groups have targeted oil pipelines there in the past.
It also mentioned Shahriar, a suburb of Tehran where Amnesty said there had been "dozens of deaths". It described the suburb as likely one of the areas with the highest death tolls in the unrest.
Ms Mills said there was a "general environment of fear inside of Iran at the moment".
Some families were also being forced to make extortionate payments to have the bodies of victims returned to them.
She said security personnel had also been visiting hospitals, looking for patients with gunshot wounds or other injuries from the unrest and immediately detained those with suspicious wounds.
Philip Luther, Amnesty's research and advocacy head for the Middle East, called the number of deaths "evidence that Iran's security forces went on a horrific killing spree", and called on the global community to ensure those responsible are held accountable.
Hossein Naqavi-Hosseini, a member of parliament's national security committee, said last week that about 7,000 people were arrested during the unrest. His comparison raised the rhetorical stakes surrounding the latest unrest.
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