648 killed in Iran protest: Rights Group

The massive crackdown on a wave of protests in Iran has killed at least 648 people, a rights group said on Monday, as Iranian authorities sought to regain control of the streets with mass nationwide rallies.

Rights groups have sounded the alarm over the deadly crackdown, warning an internet blackout that monitor Netblocks says has lasted more than three-and-a-half days is aimed at masking the extent of the bloodshed.

The Norway-based NGO Iran Human Rights (IHR) said it had confirmed 648 people killed during the protests, including nine minors, and thousands more injuries, but warned the death toll was likely much higher -- "according to some estimates more than 6,000", it said.

IHR added that the internet shutdown made it "extremely difficult to independently verify these reports".

It said an estimated 10,000 people had also been arrested.

"The international community has a duty to protect civilian protesters against mass killing by the Islamic republic," said IHR director Mahmood Amiry-Moghaddam.

Despite the blackout severely affecting Iranians' ability to post videos of the protests, which have rocked big cities since Thursday, one video geolocated by AFP showed dozens of bodies outside a morgue south of Tehran, with what appeared to be grieving relatives searching for loved ones.

Over two weeks of demonstrations initially sparked by economic grievances have turned into one of the biggest challenges yet to the theocratic system that has ruled Iran since the 1979 Islamic revolution ousted the shah.

Seeking to regain the initiative, the government called for rallies nationwide backing the Islamic republic on Monday.