Several Iranians who protested in Iran over the past few days have spoken to CNN about seeing enormous crowds as well as brutal violence on the streets of Tehran, with one woman saying she saw “bodies piled up on each other” in a hospital.

Demonstrations that began as outrage at the state of the economy have spread to cities across the country, amid an escalating crackdown by the authorities.

US Airlines flights suspended alongside Lufthansa flydubai Turkish Airlines AJet Pegasus Qatar Airways and Austrian Airlines as anti-government protests cripple Iran entering third week with 45-100 deaths amid internet blackouts and security crackdowns.

Iranian hospitals reportedly overwhelmed as anti-government protests rage, with doctors treating gunshot wounds to heads and eyes amid nationwide unrest.

In a serious challenge to Iran’s authoritarian government, angry protests have spread from the markets and universities of major cities to the impoverished towns in the hinterland.

Fresh demonstrations were reported late on Saturday in Tehran, the northern city of Rasht and other towns, according to the Hengaw Organization for Human Rights. Hengaw said three demonstrators were killed in the Rasht area,

A statement from the group reads: “Live metrics show Iran is now in the midst of a nationwide internet blackout; the incident follows a series of escalating digital censorship measures targeting protests across the country and hinders the public's right to communicate at a critical moment.”

Iran's Revolutionary Guards warned on Saturday that safeguarding security was a "red line" and the military vowed to protect public property, as the clerical establishment stepped up efforts to quell the most widespread protests in years.