Amnesty International says more than 1 million people in over 200 countries and territories across the world have signed a petition calling on the Iranian authorities to release prominent human rights lawyer Nasrin Sotoudeh.
She has been sentenced to a total of 38 1/2 years in prison and 148 lashes following what the London-based human rights watchdog called "two grossly unfair trials."
To mark one year since her arrest, Amnesty International says it is organizing on June 13 a handover of the signatures collected to Iranian embassies around the globe.
Sotoudeh's detention "has exposed the depths of the Iranian authorities' repression on an international stage," Philip Luther, the group's research and advocacy director for the Middle East and North Africa, said in a statement.
"Today we are sending them a clear message: the world is watching and our campaign will continue until Nasrin Sotoudeh is free," Luther added.
Sotoudeh, the co-winner of the European Parliament's 2012 Sakharov Prize for Freedom of Thought, was arrested at her home in Tehran on June 13 last year.
The human rights lawyer and women's rights defender was sentenced in March to 33 1/2 years in prison and 148 lashes.
In September 2016, Sotoudeh had been sentenced in her absence to five years in prison in a separate case.
Taking both cases together, the total prison sentence against the lawyer is 38 1/2 years. Under Iran's sentencing guidelines, she is due to serve 17 years in prison.
Sotoudeh's case is "emblematic of a wider crackdown by the Iranian authorities in the last few years to quash Iran's civil society and silence those advocating for human rights" in the country, according to Amnesty International.
Sotoudeh last year represented several of the women detained for removing their head scarves in public to protest against the country's Islamic dress code.
An outspoken critic of the Iranian establishment, she previously spent three years in prison after representing dissidents arrested during mass protests in 2009 against the disputed reelection of President Mahmud Ahmadinejad.
She has denied all charges against her.