Protesters stage an illegal rally in Tehran on Saturday in protest of the result and process of the presidential election.
Tehran's prosecutor general's office has said that some armed saboteurs opened fire on civilians and killed people in post-election violence in Tehran.
"A number of Tehrani citizens were shot dead by unknown vandals Saturday night," said the office on Monday.
It said security forces have arrested an armed man involved in Saturday's riots but rejected reports over the arrest of an armed man whose photo was released by some news agencies.
"Iran's security and intelligence officials are currently probing into the identity of the individual whose photo was published and broadcast by news agencies," it added.
This is while the situation in Tehran is back to normal for the second consecutive day on Monday. On Saturday, 'terrorist elements'-who had infiltrated the rallies --created the most violent day of protests by setting fire on a mosque and two gas stations as well as killing a number of people.
Despite warnings by Iranian police, protesters staged illegal rallies in Tehran for several days to cry foul over what they call 'vote-rigging' in Iran's presidential election.
Supporters of the defeated candidate Mir-Hossein Moussavi have held illegal street protests in Tehran and some other cities since the re-election of President Mahmoud Ahmadinejad on June 12.
Presidential contenders Mir-Hossein Moussavi and Mehdi Karroubi reject the result as fraudulent and demand a re-run.
On Saturday, acting Police Chief Brigadier General Ahmad-Reza Radan warned against any illegal gatherings, saying police would firmly deal with any illegal rallies from now on and those who plan such activities would be prosecuted.