A US state department official on Thursday said that 1,000 or more protesters were killed during weeks of unrest in Iran.
US Special Representative for Iran, Brian Hook, said that Irans have sent the State Department 32,000 videos and photos documenting the carnage since Secretary of State Mike Pompeo appealed last month for them to do so.
One of the videos shows protesters being mowed down by troops firing machine guns mounted on trucks, he said.
Hook said that Trump administration will ask Congress to impose harsh sanctions on officials responsible for alleged atrocities and mistreatment of thousands of protesters.
"As the truth is trickling out of Iran, it appears the regime could have murdered over 1,000 Iran citizens since the protests began," including at least a dozen children, Hook said at a State Department briefing.
The United States believes that many thousands more have been wounded and that at least 7,000 people have been arrested, he said.
The protests in Iran began last month after the government announced an increase in gas prices, leading to discontent among the people. Since then, citizens have taken to the streets and are calling for the removal of leaders.
In November, US Secretary of State Michael Pompeo said that Washington backs the Iran protestors and condemned Tehran's call to snap internet access in various parts of the country.
"The United States hears you, we support you, and we will continue to stand with you in your struggle for a brighter future for your people and for your great nation," Pompeo had said.
The protests in Iran are widely seen as economic discontentment gripping the Middle East ever since the Trump administration took a hardline stance against Tehran.
In May last year, Trump announced the US' withdrawal from the 2015 nuclear deal, or the Joint Comprehensive Plan of Action (JCPoA), which granted sanctions relief to Iran in exchange for curbs on its nuclear programme.
Since then, his administration has slapped a multitude of sanctions targetting the Iran economy and some of its leaders.
( With inputs from ANI )