Iran on Monday reportedly carried out the first executions of activists detained in street protests after the disputed 2009 presidential poll, hanging two men it said were from an outlawed group.

The executions of two activists from the Iranian exiled opposition group, People's Mujahedeen of Iran (PMOI) came despite a plea by US Secretary of State Hillary Clinton that they be freed.

The Tehran prosecutor's office named the executed pair as Jafar Kazemi and Mohammad Ali Hajaghaei. It did not say where they were hanged.

"Two elements of the Monafeghin (hypocrites) group named Jafar Kazemi... and Mohammad Ali Hajaghaei ... were executed early today," the prosecutor's office said on its website, referring to PMOI, which once ran an armed group in Iran.

On August 10, US Secretary of State Hillary Clinton had urged the Iranian authorities to release the two activists, despite the PMOI being on Washington's list of foreign terrorist organisations.

The prosecutor's office said "these two hypocrites were members of an active network of the said group and were involved in the (post-election) riots under the guidance of their ringleader in England."

"The convicts had resorted to distributing pictures and banners related to the Monafeghins, taking photos and films of the clashes as well as chanting slogans in favour of the group."

The 2009 presidential election result triggered widespread anti-government demonstrations in Tehran.

Dozens of protesters were killed, scores wounded and thousands jailed when security forces clashed with them after the announcement of the election result, which Ahmadinejad's rivals claim was rigged in his favour.

Clinton had urged that those rounded up, including Kazemi and Hajaghaei, be freed.

"We are also concerned about the fate of Iranians who are in danger of imminent execution for exercising their right to free expression after the June 2009 elections," Clinton said on August 10 in a statement, naming Kazemi and Hajaghaei.

Her plea for the release of the two activists came despite Washington retaining the PMOI on its list of foreign terrorist organisations, even as the European Union took it off its own similar list in 2009.

In a statement released in France, Maryam Rajavi, head of National Council of Resistance of Iran of which PMOI is a wing, condemned what she said were "barbaric executions" of the activists, adding the international community must "suspend economic and diplomatic ties with the ruling medieval regime" of Iran.

The Tehran prosecutor's office said Hajaghaei had a history of travelling to Iraq, where the PMOI's main camp is based.

"While staying there for a few months, he received 3,000 dollars and training sessions from the Monafeghins in Camp Ashraf," the office said, referring to the PMOI camp located in the Iraqi province of Diyala.

It said the other condemned man, Kazemi, had confessed to his activities during the post-election unrest.

"Kazemi admitted putting up pictures supporting members of the terrorist Monafeghin group as well as filming the street protests in Azadi (Freedom) Square and Enqelab (Revolution) Street" in Tehran, it said, referring to venues where bulk of brutal post-election unrest occurred.

Two weeks ago, Kazemi's wife Roudabeh Akbari told opposition website, Rahesabz that her husband's imminent execution "was unfair," adding he had simply visited Camp Ashraf to see his son.

Iran has sentenced around a dozen activists to death for their role in the post-poll unrest.

Six of the sentences have been upheld, according to Tehran prosecutor Abbas Jafar Dolatabadi, with the hangings on Monday reportedly the first to be carried out.

Dolatabadi said in May that Kazemi and Hajaghaei were arrested in September 2009. The other four on the death row are also said by the authorities to be members of PMOI.

The PMOI is responsible for several acts of violence against Iranian civilians and government officials.

It was set up with an aim of replacing firstly the shah and then the Islamic clerical regime of Iran.

PMOI is known to have participated with former Iraqi dictator Saddam Hussein's forces during their war with Iran in the 80s.

The members of Camp Ashraf were disarmed after the 2003 invasion of Iraq by US-led forces.