More than two dozen Iranian journalists are among the hundreds of people being imprisoned by the hardline government in Tehran as part of the violent post-election crackdown, according to Amnesty International.

As many as 30 journalists remain in detention, according to the human rights group, which calls the arrested reporters "prisoners of conscience".

Mass gatherings have waned into scattered protests as the Iranian clergy which rules the country tightened its repression of opponents since the bitterly disputed election.

Foreign news journalists have been banned from the streets, and some foreign reporters have been expelled from the country. Two journalists reporting for foreign news outlets have also been arrested, according to Amnesty: Maziar Bahari of Newsweek, on June 21, and Iason Athanasiadis-Fowden of The Washington Times, who was arrested on or around June 19.

About 20 of 25 employees of the Iranian newspaper Kalameh Sabz were arrested at their office on June 22. Their whereabouts remain unknown, according to Amnesty. Opposition presidential candidate Mir Hossein Mousavi established the newspaper earlier this year.

Amnesty International spokeswoman Sharon Singh said Amnesty has at least two sources on each of the arrests. In many cases family members bring their problems to the organisation.

"If nothing else, the authorities must immediately disclose the whereabouts of these journalists, ensure that they are not tortured or otherwise ill-treated and allow their families and lawyers access to them," said Hassiba Hadj Sahraoui, Amnesty's deputy director for the Middle East and North Africa.

"Unless the authorities lift all unlawful restrictions on freedom of expression, which includes the right of journalists to report on events, and release all the journalists arrested, we can only assume they are trying to hide evidence of abuse and further silence any critical voice," Sahraoui added.

Keyvan Samimi Behbehani, editor of the banned Nameh magazine, was arrested at home, the group said. He is a member of the Centre for Human Rights Defenders' Arbitrary Arrests Committee.

Also arrested was Mohammad Ghochani, the editor of Etemad-e Melli. Amnesty International believes he is held in a Ministry of Intelligence prison.