Eleven of Iran's most prominent political prisoners, including human rights lawyer Nasrin Sotoudeh, have been unexpectantly freed by authorities in Iran days before President Hassan Rouhani's first speech to the United Nations.

Sotoudeh was released on Wednesday evening along with 10 others detained after unrest that followed the disputed 2009 re-election of 2009 Mahmoud Ahmadinejad.

Sotoudeh, who was serving six years for “acting against national security”, told the New York Times: “I don’t know why they released me. I don’t know under what legal basis they released me. But I am free.”

Sotoudeh's husband, Reza Khandan, told the Reuters news agency that his wife was dropped off at their home by prison authorities "It's not temporary, it's freedom," Khandan said. "We are all so happy from the depths of our hearts."

Sotoudeh was arrested in September 2010 and convicted of spreading propaganda and conspiring to harm the state.

She staged a 50-day hunger strike last year to protest against the authorities' treatment of her daughter, who was subjected to a travel ban.

"Psychologically, my condition is very good but my experience - with all the psychological pressure, the tense security atmosphere, and not having access to make phone calls - was very tough," she told the AFP news agency after her release.

The release of the dissidents come less than a week before President Rouhani addresses the UN General Assembly for the first time and is expected to present a less confrontational image than Ahmadinejad, under whose eight years in power Iran came under ever-tougher Western trade sanctions.

Rouhani pledged during his election campaign to ease some political and social restrictions, and his supporters have called for the release of political prisoners.

Prior to her arrest, Sotoudeh had defended journalists and rights activists including Nobel Peace laureate Shirin Ebadi.

She also represented Zahra Bahrami, a woman with dual Iranian and Dutch nationality who was hanged in January 2011 on drug-trafficking charges.

Source: Agencies