Amnesty International said the "alarming death toll" was further evidence that Iran's security forces went on a "horrific killing spree."
More than 200 people are believed to have been killed in Iran in the last month during protests over a hike in government-set gasoline prices and a crackdown that followed, according to a report published by human rights group Amnesty International.
"This alarming death toll is further evidence that Iran's security forces went on a horrific killing spree that left at least 208 people dead in less than a week," said Philip Luther, research and advocacy director for the Middle East at Amnesty International, in a statement published alongside the report on Monday.
Amnesty International said it verified extensive footage that showed security forces shooting at unarmed protesters.
It added that it had compiled the death toll by interviewing and crosschecking a range of sources inside and outside Iran including victims' relatives, journalists and human rights activists involved in gathering the information.
NBC News could not independently verify the number of dead.
Iran's mission to the United Nations disputed Amnesty's findings early Tuesday though it offered no evidence to support its claim.
The report came hours before Iranian state television acknowledged on Tuesday that security forces shot and killed what it called "rioters" in multiple cities — the first time that authorities have offered any sort of accounting for the violence they used to put down the demonstrations.
The acknowledgment came in a television package that criticized international Farsi-language channels for their reporting on the crisis, which started on Nov. 15and has seen minimum prices for government-subsidized gasoline rise by 50 percent.
Cheap gasoline is widely expected by consumers in Iran, home to the world's fourth-largest crude oil reserves.
The state TV report sought to describe killings in four categories, alleging some of those killed were "rioters who have attacked sensitive or military centers with firearms or knives, or have taken hostages in some areas." The report described others killed as passers-by, security forces and peaceful protesters, without assigning blame for their deaths.
State TV acknowledged confronting "rioters" in Tehran. It also mentioned Shahriar, a suburb of Tehran where Amnesty on Monday said there had been "dozens of deaths." It described the suburb as likely one of the areas with the highest toll of those killed in the unrest.
Amnesty offered no breakdown for the deaths elsewhere in the country, though it said "the real figure is likely to be higher."
Mansoureh Mills, an Iran researcher at Amnesty, said there was a "general environment of fear inside of Iran at the moment."
"The authorities have been threatening families, some have been forced to sign undertakings that they won't speak to the media," she said.
Authorities also have been visiting hospitals, looking for patients with gunshot wounds or other injuries from the unrest, Mills said. She alleged that authorities then immediately detain those with suspicious wounds.
Iran's U.N. mission in New York called Amnesty's findings "unsubstantiated," without elaborating.
"A number of exile groups (and media networks) have either taken credit for instigating both ordinary people to protest and riots, or have encouraged lawlessness and vandalism, or both," said Alireza Miryousefi, a spokesman at the mission.
Iran has yet to release any nationwide statistics over the unrest that gripped the Islamic Republicand the scale of the demonstrations remains unclear. One Iranian lawmaker said he thought that over 7,000 people had been arrested. Iran's top prosecutor disputed that figure without offering his own.
Authorities shut down internet access amid the demonstrations, blocking those inside the country from sharing their videos and information, as well as limiting the outside world from knowing the scale of the protests and violence.
While not drawing as many Iranians into the streets as those protesting the disputed 2009 presidential election, the gasoline price demonstrations rapidly turned violent faster than any previous rallies. Widespread economic discontent has gripped the country since May last year, when President Donald Trump imposed crushing sanctions after unilaterally withdrawing from Tehran's nuclear dealwith world powers.
The demonstrations began after authorities raised minimum gasoline prices to 15,000 Iranian rials per liter, an equivalent of about 50 cents a gallon. After a monthly 60-liter quota, it costs 30,000 rials a liter. That's nearly 90 cents a gallon. An average gallon of regular gas in the U.S. costs $2.58 by comparison, according to AAA.
Iranians have already seen their savings chewed away by the rial's collapse from 32,000 to $1 at the time of the 2015 nuclear accord to 126,000 to $1 today. Daily staples also have risen in price.