I saw it with my own eyes - they fired directly into lines of protesters, and people fell where they stood.
Omid's voice was shaking as he spoke, fearful of being traced. Breaking the wall of silence between Iran and the rest of the world takes immense courage, given the risk of reprisals by the authorities.
Omid, in his early 40s and whose name we have changed for his safety, has been protesting on the streets of a small city in southern Iran over the past few days against worsening economic hardship.
He said security forces had opened fire at unarmed protesters in his city with Kalashnikov-style assault rifles.
We are fighting a brutal regime with empty hands, he said.
The BBC has received similar accounts of the crackdown by security forces following the widespread protests across the country last week. Since then, internet access has been cut by the authorities, making reporting from Iran more difficult than ever. BBC Persian is banned from reporting inside Iran by the government.
One of the largest nationwide anti-government protests took place on Thursday, the twelfth night of demonstrations. Many people appear to have joined the protests on Thursday and Friday after calls from Reza Pahlavi, the exiled son of the last shah of Iran who was overthrown in the 1979 Islamic revolution.
The following day, Iran's Supreme Leader Ali Khamenei said: The Islamic Republic will not back down. It appears that the worst bloodshed occurred after that warning as security forces and the Islamic Revolutionary Guard Corps take their orders from him.
Eyewitnesses in Fardis, a city just to the west of Tehran, said that on Friday, members of the paramilitary Basij force under the Islamic Revolutionary Guard Corps (IRGC) suddenly attacked protesters after hours without a police presence on the streets.
Those who have given accounts to BBC Persian say the reality inside Iran is hard for the outside world to imagine, and the death toll reported by international media so far only represents a fraction of their own estimates.
International news outlets are not allowed to work freely inside Iran and they are mostly relying on Iranian human rights groups who are active outside the country. On Monday, the Norway-based Iran Human Rights (IHRNGO) said at least 648 protesters in Iran had been killed, including nine people under the age of 18.
UN Secretary-General António Guterres said on Sunday that he was shocked by reports of violence and excessive use of force by the Iranian authorities against protesters resulting in deaths and injuries in recent days.
Graphic videos published on the activist-run Telegram channel Vahid Online on Sunday showed a large number of bodies at the Kahrizak Forensic Medical Centre in Tehran, with many families either mourning or attempting to identify the corpses. In one of the videos apparently from Kahrizak, a photo of a body relatives are seen looking at the photos of unidentified bodies displayed on a screen.
The increasing violence has led to rising fears among the population, with many now chanting messages of protest from inside their homes rather than taking to the streets. Eyewitness accounts describe a rapidly deteriorating situation where security forces are seen using live ammunition against civilians.
