Individuals reportedly had contact with the Monafeghin, better known as the People's Muahadeen.
Three people arrested after Iran's disputed presidential election have been condemned to death, despite a global outcry over trials of people who claimed Mahmoud Ahmadinejad's re-election was rigged."Three people who were accused (for their role) in the post-election incidents have been sentenced to death," said Zahed Bashiri Rad, media officer at the justice ministry, quoted by ISNA news agency on Saturday.
Bashiri Rad, giving only the initials of the convicts said that "MZ and AP were convicted for ties with the Kingdom Assembly of Iran and NA for ties with the Monafeghin (exiled opposition group commonly known as the People's Mujahedeen)."
Massive street protests broke out in Iran following Ahmadinejad's re-election.
About 4,000 people were arrested, and 140 of them, including senior reformers and journalists, have been put on trial for seeking a "soft" overthrow of the regime and for inciting protests.
On Thursday, a reformist website reported that a member of a group seeking to restore Iran's monarchy has been sentenced to death for his involvement in the unrest, identifying him as Mohammad Reza Ali Zamani.
Judiciary officials were not available to confirm if he was the "MZ" mentioned by ISNA on Saturday.
On Friday, Amnesty International urged Tehran to lift the death sentence on Zamani. A member of the Kingdom Assembly of Iran, he was among scores of arrested people in the post-vote mass demonstrations, it said.
Amnesty condemned such "show trials" as a "mockery of justice".
The London-based group said it "fears that Zamani's death sentence will pave the way for more death sentences against those being tried on similar offences.
"Amnesty International is calling on the Iranian authorities to immediately halt all scheduled executions and to commute all death sentences," it added.
Bashiri Rad said the death sentences were "not final and they can still be appealed to the supreme court."
Under Iranian law, convicts may appeal their sentences, which must be upheld by both the appeals court and the supreme court before they are carried out.
Bashiri Rad also said some other defendants received their sentences and they have appealed, but did not give the details of the verdicts.
"Appeals of 18 of defendants that have been convicted over the recent riots will soon be sent to the Tehran appeals court," Bashiri Rad said.
Tehran prosecutors have denied a report that 20 people, among them prominent reformists, including Iranian-American scholar Kian Tajbakhsh and reformist politicians Mohammed Ali Abtahi, Mohammad Atrianfar, Shahab Tabatabaei, Saeed Shariati and Abdollah Momeni will soon be freed on bail.
Bashiri Rad did not specify if among the 18 there were any prominent reformists.
Reformist websites say the government continues to arrest its opponents, and there are also strong calls by various hardliners for the arrest and trial of Ahmadinejad's main challengers in the poll, Mir Hossein Mousavi and cleric Mehdi Karroubi.