A U.S.-based rights organization said Sunday it has confirmed at least 3,766 deaths linked to Iran’s nationwide protests and warned the true toll from the crackdown could be far higher.

The Human Rights Activists News Agency posted the revised figure, increasing its previous toll of 3,308. The death toll exceeds that of any other round of protest or unrest in Iran in decades, and recalls the chaos surrounding the 1979 revolution.

The agency has been accurate throughout the years of demonstrations in Iran, relying on a network of activists inside the country that confirms all reported fatalities. The Associated Press has been unable to independently confirm the toll.

Iranian officials have not given a clear death toll, although on Saturday, the country's Supreme Leader Ayatollah Ali Khamenei said the protests had left "several thousand" people dead - and blamed the United States for the deaths. It was the first indication from an Iranian leader of the extent of the casualties from the wave of protests that began Dec. 28 over Iran's ailing economy. The Human Rights Activists News Agency says 24,348 protesters have been arrested in the crackdown.

‘Tantamount to all-out war’