"The Act of Killing," a critically acclaimed documentary in which a pair of gangsters re-enact their roles in the 1965 Communist purges in Indonesia, will be honored on Sunday with two awards at the Berlin International Film Festival.

Director Joshua Oppenheimer's film will take home the Panorama Audience Award and the Ecumenical Jury prize, the latter of which is awarded by a six-person jury to "directors who have succeeded in portraying actions or human experiences that are in keeping with the Gospels, or in sensitizing viewers to spiritual, human or social values."

The film first gained international attention when it screened at the Toronto Film Festival in September, where it was lauded for its unconventional presentation of the tragedy. Its principle subject, Anwar Congo, was a small-time gangster with a passion for Hollywood Westerns in 1965 when he was enlisted to participate in the mass killing of Indonesians alleged to have Communist loyalties.

In "The Act of Killing," the unpunished Medan-based men act out their state-sponsored crimes in a variety of film genres, describing their roles unapologetically, and with an honesty that the Indonesian government has not yet been willing to show. Estimates put the number of those killed in the purges at anywhere from 500,000 to two million people, at a tumultuous time in the country's history.

In a statement, the Ecumenical Jury praised "The Act of Killing" for the present-day value it brought to an historical event.

"This deeply unsettling film exposes the evil mass murders which took place in Indonesia in 1965 and reveals the monstrosity of these crimes. It re-opens a deep wound with the conviction that it is worthwhile to unearth such atrocities," the jury said.

The filmmakers struck a similar chord in an acceptance speech posted to the documentary's Facebook page.

"Since International Human Rights Day on December 10, 2012, 'The Act of Killing' has screened hundreds of times in Indonesia, in more than 90 cities. It has helped give rise to a national conversation in which, finally, the silence around the genocide has been broken, and Indonesians are openly discussing how today's regime of corruption and fear is built on a mountain of corpses.

"We thank the Ecumenical Jury for this prize: it is an important contribution to our effort to break the silence. In itself, this award exposes lies that have, for so long, been used to justify crimes against humanity, to stigmatize survivors, to keep people afraid."

At the time of writing on Sunday, the official website of "The Act of Killing" could not be accessed in Indonesia.