Tehran, May 14 (IANS): Renowned Iranian reformist Mostafa Tajzadeh on Friday announced his candidacy for the upcoming presidential election, the first time a regime critic has registered for the post in the Islamic Republic.

"I was a political prisoner myself for seven years and am, therefore, first and foremost against banning critics from speaking up," dpa news agency quoted Tajzadeh said as saying.

The former Deputy Interior Minister, under President Mohammad Khatami, belongs to the radical wing of the reformist camp.

After protesting against the allegedly rigged election of Mahmoud Ahmadinejad in 2009, Tajzadeh was arrested and spent several years in prison.

Since then, the 64-year-old has been frequently in the headlines with his tweets criticising the regime.

During the registration of his candidacy, Tajzadeh said he was against forcing women to wear a headscarf.

He said he wanted to promote more liberties and seek peaceful solutions to foreign policy issues.

Like all other candidates, Tajzadeh still has to be vetted and approved by the Guardian Council.

His approval is seen as highly unlikely, however.

Registration for the presidency is open until Saturday.

Aside from former leader Ahmadinejad, several former generals of the revolutionary guard have announced their bid.

Justice chief Ebrahim Raisi is seen as the most promising candidate.

Incumbent President Hassan Rouhani cannot stand for re-election after two terms in office.

The election is to take place on June 18.