Official media in Iran report 15 people have been killed in riots that rocked the capital Tehran during massive anti-government rallies.
State television said 10 of those killed during Sunday's fierce clashes were members of what it called anti-revolutionary terrorist groups, apparently referring to anti-government protestors, the AFP reports.
The other five who died were killed by terrorist groups in a suspicious act, the report said, without elaborating.
Clashes between opposition supporters and police continued into the night following a day of protests in Tehran and several other cities.
Earlier, opposition websites and witnesses said eight people were shot dead by security forces; four in Tehran and four in the northern city of Tabriz.
Iranian police confirmed that people had died, but denied the victims were shot by police.
Among the dead was opposition leader Mirhossein Mousavi's nephew. State television said unknown assailants had killed Ali Habibi Mousavi.
His funeral this week is thought likely to be a focal point for more protests, the BBC reports.
According to Mr Mousavi's website, his nephew was shot in the back as security forces fired on demonstrators.
On Monday, the state-owned English-language Press TV said eight people had died. Earlier, Persian state television had reported at least 15 people killed.
Thousands of demonstrators are reported to have taken part in the anti-government protests, in defiance of official warnings. The state broadcaster says about 300 people were arrested.
Opposition websites say that in some parts of the city, police officers refused to carry out orders to fire into crowds of demonstrators.
Call to protest on holy festival
The opposition has used the Shi'ite Moslem festival of Ashura to call large numbers of people onto the streets to challenge the government.
The fatalities are the first in street protests since the demonstrations immediately after the June presidential election, in which the opposition says more than 70 people were killed.
The United States and France have condemned the violent clashes in Iran.
The White House has described the killings and arrests as the unjust suppression of civilians.