At least 146 demonstrators were killed across Iran since its leaders ordered security forces to stamp out protests that followed fuel price rises on November 15, Amnesty International said on Monday, according to AFP.
"According to credible reports... those killed include at least 143 people. The deaths have resulted almost entirely from the use of firearms," the London-based group said.
One person reportedly died after inhaling tear gas, another after being beaten. Amnesty "believes that the death toll is significantly higher" and was still investigating, it said.
Amnesty, which last week gave a death toll of 106, called for the international community to condemn the bloodshed.
The unrest erupted hours after it was announced that the price of gas would rise to 15,000 rials per liter (12 US cents) from 10,000 for the first 60 liters, and to 30,000 rials for any extra fuel bought after that each month.
Iran has blamed “thugs” linked to exiles and foreign foes - the United States, Israel and Saudi Arabia - for stirring up unrest following hikes in gasoline prices.
Iran’s Revolutionary Guards have arrested about 100 leaders of the protests and said they would act to severely punish them.
"The international community's cautious and muted response to the unlawful killing of protesters is woefully inadequate," said Philip Luther, Amnesty's research and advocacy head for the Middle East.
"They must condemn these killings in the strongest possible terms and describe these events for what they are- the deadly and wholly unwarranted use of force to crush dissent," he added.
Amnesty said "verified videos show security forces deliberately shooting unarmed protesters from a short distance. In some cases, protesters were shot while they were running away".
They also showed security forces shooting from rooftops, it said, adding that the crackdown was carried out by police, Revolutionary Guards, and the Basij paramilitary force "and others".