Iranian authorities arrested, jailed and sometimes executed 1.7 million people around the capital Tehran alone in the first 30 years after the 1979 Islamic revolution, Media advocacy group Reporters Without Borders said on Thursday.

The organisation revealed its count that included regime opponents, Bahais and other religious minorities and at least 860 journalists as Iran marked the 40th anniversary of its revolution.

The group said at a news conference in Paris that its information was based on a confidential file of judicial proceedings obtained by whistleblowers that covered the years 1979 to 2009.

The file registering judicial procedures contains details on some 1.7 million people, including minors, locked up in Evin prison in the first three decades of the Islamic regime that overthrew Shah Mohammad Reza Pahlavi, shaking the region and the world.

Among the journalists, at least four were executed, according to RSF, as the watchdog group is known. The organisation noted that the detailed Iranian file never mentions the professional status of individuals, suggesting this made it easier for the regime to claim it wasn't holding journalists or, more broadly, prisoners of conscience.

“The very existence of this file and its millions of entries show not only the scale of the Iranian regime’s mendacity for years when claiming that its jails were holding no political prisoners or journalists, but also the relentless machinations it used for 40 years to persecute men and women for their opinions or their reporting,” RSF head Christophe Deloire said.

RSF set up a committee that combed through the Iranian file. It is headed by 2003 Nobel Peace Prize Laureate Shirin Ebadi, an Iranian human rights lawyer.

The file reveals some previously undisclosed information, RSF said. "After months of verification, we have identified in these files of 1.7 million records, the cases of at least 61,940 political prisoners during the period of 1979 until 2009, only in Tehran," said Mr Deloire.

Of these, 520 were aged between 15 and 18, he said.

Mr Deloire said the files show the "relentless machinations" used "to persecute men and women for their opinions or their reporting."

Of the 61,924 women in the register register, 218 were journalists.

RSF is referring "these state lies" to the UN human rights commissioner, Michelle Bachelet, "so that Iran can be held to account," he said.

According to RSF, state control of news and information has been relentless in Iran for the past 39 years. The country is ranked 164 of 180 nations according to RSF’s 2018 World Press Freedom index.

“The Islamic Revolution keeps a tight grip on most media outlets and never relents in its persecution of independent journalists, citizen-journalists, and media outlets,” RSF says on its website.

The country “uses intimidation, arbitrary arrest, and long jail sentences imposed by revolutionary courts at the end of unfair trials. The media that are still resisting increasingly lack the resources to report freely and independently.”

Evin prison in north Tehran was built by the last Shah of Iran to hold his jailed opponents. After the 1979 revolution, the prison grew to hold up to 15,000 detainees at its peak.