"It appears the regime could have murdered over 1,000 Iranian citizens since the protests began," Brian Hook, the US pointman on Iran, told reporters.

He acknowledged that information was difficult to verify but said: "We know for certain it is many, many hundreds."

Hook said that "many thousands" of Iranians have been wounded and that at least 7,000 protesters have been detained.

Protests broke out on November 15 in Iran, which is under sweeping sanctions from the United States, after the government abruptly hiked fuel prices.

Hook said the ensuing crackdown showed that the regime has had to rely on brute force and was losing support even with its traditional working-class base.

"This is the worst political crisis the regime has faced and its 40 years," Hook said.

His death toll is sharply higher than the figure of 208 dead given by Amnesty International, which said that the figure may be higher but that it was cautious due to the difficulties in verifying information.

The United States, which considers Iran's regime its top enemy, has appealed for Iranians who can circumvent restrictions on the internet to send footage of the protests.

Hook said the United States has received photos or videos from 32,000 people and was basing its estimate on their information, as well as reports from outside groups.

Iran has dismissed the high death tolls reported by foreign sources as "utter lies" and has so far confirmed only five dead -- four security force personnel killed by "rioters" and one civilian.