New Delhi, Jan. 20 -- A U.S.-based activist agency said Sunday it has verified at least 3,919 deaths during a wave of protests that swept Iran and led to a bloody crackdown, and fears the number could be significantly higher.

The Human Rights Activists News Agency posted the revised figure, up from the 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 ...