Iranian security forces may have killed more than 1,000 people since protests began over the government's decision to raise fuel prices, according to a top State Department official, Anadolu Agency reports.
"We can't be certain because regime blocks information," US Special Representative for Iran Brian Hook told a press conference at the State Department.
At least a dozen children, including 13- and 14-year-olds were killed, said Hook.
He also said the State Department has seen a video of one incident in which more than 100 people were killed.
"When it was over, the regime loaded the bodies into trucks. We do not yet know where these bodies went. But we are learning more and more about how the Iranian regime treats its own people," he added.
Demonstrations broke Nov. 15 out across Iran after the government imposed petrol rationing and raised fuel prices by at least 50%.
Earlier this week, Philip Luther, research and advocacy director for the Middle East and North Africa at Amnesty International, said at least 208 people were killed since protests began.
"This shocking death toll displays the Iranian authorities' shameful disregard for human life," said Luther on Monday.
At least 100 banks and dozens of shops have been set ablaze during the protests, the semi-official Mehr news agency said, quoting security officials.
Though there are no official figures on the arrests, but the Fars news agency said more than 1,000 protesters have been arrested.
Iran's elite Revolutionary Guards threatened to take "decisive" action against protesters if they "disturb people's peace and security."