UPDATE: Martin Scorsese, who spoke out in support of Jafar Panahi both when he was first arrested and right after he was convicted, has added his support to the petition being circulated by Amnesty International. His participation is reflected in the amended release below.

EARLIER: Amnesty International has gotten involved in protesting the 6-year prison sentence given to Iranian filmmakers Jafar Panahi and Mohammad Rasoulof. As Deadline revealed last week, the human rights advocate has enlisted Paul Haggis, Sean Penn and Harvey Weinstein to spearhead the petition effort meant to create international pressure as the filmmakers prepare their appeal. Here’s the formal announcement:

(New York) — Academy Award winners Paul Haggis, Martin Scorsese and Sean Penn, along with film producer and movie studio chairman Harvey Weinstein, have joined forces with British-Iranian actress and Amnesty International USA (AIUSA) spokesperson Nazanin Boniadi to condemn the harsh sentence imposed on distinguished Iranian film director Jafar Panahi.

Both Panahi and his artistic collaborator, Mohammad Rasoulof, have been given six-year prison sentences after being convicted of “propaganda against the state.” Panahi was also sentenced with a twenty-year total ban on artistic activities. The Hollywood greats have signed a petition, which Boniadi initiated with AIUSA, to urge Iranian authorities to overturn Panahi’s sentence –and encouraged others to go to http://www.amnestyusa.org to do the same.

“As someone who has often gotten in trouble for opening his mouth, it is hard to fathom the idea of being incarcerated for six years simply for speaking my mind, or to be banned from making films for 20 years,” said Haggis, who is best known for becoming the first screenwriter to write two Best Film Oscar winners back-to-back: “Million Dollar Baby” and “Crash.”

Haggis, the founder of Artists for Peace and Justice, added, “If this happened to me, I would hope my colleagues would speak out in my name, as we are compelled to speak out in Jafar’s. I urge the Iranian authorities to overturn Mr. Panahi’s inhumane and unjust sentence. I ask that people across the world join Sean Penn, Martin Scorsese, Harvey Weinstein and myself in signing the Amnesty International petition calling for the immediate reversal of the sentence against Jafar Panahi and Mohammad Rasoulof.”

Haggis has initiated a white ribbon campaign—urging actors, producers, writers and directors to wear white ribbons during public appearances, to protest the travesty of justice inflicted on his colleagues. Haggis highlighted the campaign and petition at a press conference today at the Capri Hollywood Film Festival, where he is receiving a humanitarian award.

“The persecution that Panahi and Rasaulof are experiencing simply shouldn’t exist in this day and age,” said Larry Cox, executive director of AIUSA. “Their cases, and the campaign waged by Boniadi, Haggis, Penn, Scorsese, Weinstein and others, are emblematic of the work that Amnesty International has tackled head-on over its 50-year history. We are honored and grateful to have their support as we fight for Panahi and Rasaulof’s freedom.”

Prominent Iranian filmmaker Mohsen Makhmalbaf and legendary Iranian pop singer Googoosh have also signed the Amnesty International petition.

Also involved in the campaign is Iranian-American journalist and former Amnesty International prisoner of conscience Roxana Saberi, who was once held in Iran’s notorious Evin prison on trumped-up charges of espionage. She was freed after Amnesty International and other organizations rallied for her unconditional release. Since then, she has been calling for the release of other prisoners of conscience in Iran.

Jafar Panahi is the director of such masterpieces of Iranian cinema as “Badkonake Sefid” (White Balloon), “Dayareh” (Circle), for which he won the Golden Lion at the 2000 Venice Film Festival, “Talayeh Sorkh” (Crimson Gold), and “Offside.” Although invited to be a judge at the May 2010 Cannes International Film Festival, he was not able to attend as he was in detention in Evin Prison in Tehran. His absence was marked by an empty chair placed prominently on the stage for the duration of the festival.

Panahi has also been banned from carrying out his artistic work as a director, screenwriter, and film producer, from traveling abroad, and even from speaking to the media for an unimaginable period of twenty years. Panahi was convicted by a Revolutionary Court in Tehran for having exercised his right to peaceful freedom of expression through his filmmaking and political activism. He was charged with making a film deemed to be against the government, and for his alleged involvement in inciting protests following last year’s presidential election.

The right to freedom of expression is guaranteed by the International Covenant on Civil and Political Rights, which the Iranian government is party to and is obliged to uphold.

Actress Nazanin Boniadi has been a spokesperson for AIUSA since 2009 and was involved in the campaign to free Roxana Saberi. She also collaborated on The Neda Project, which commemorated the first anniversary of the murder of Neda Agha-Soltan in the streets of Tehran by a government agent in June 2009, and has been involved in supporting women’s rights on a global scale by endorsing and raising awareness on the International Violence Against Women Act (I-VAWA).

Amnesty International is a Nobel Peace Prize-winning grassroots activist organization with more than 2.8 million supporters, activists and volunteers who campaign for universal human rights from more than 150 countries. The organization investigates and exposes abuses, educates and mobilizes the public, and works to protect people wherever justice, freedom, truth and dignity are denied.