A new documentary on massacres by Zimbabwe's military has led to harsh exchanges as the 1980s killings challenge a new president who preaches unity but refuses to apologise for his alleged role in one of the country's deepest wounds.The screening in the capital, Harare, would have been almost impossible under former leader Robert Mugabe, who led the country for 37 years and resigned following military intervention in November.President Emmerson Mnangagwa, a longtime Mugabe loyalist and enforcer who succeeded him, has tolerated documentaries and plays critical of the government amid promises of a "flowering of democracy."But none has taken such direct aim at Mnangagwa as the new documentary on the army operation he supported as state security minister between 1983 and 1987. "Gukurahundi genocide: 36 years later" is named after that campaign.During Operation Gukurahundi — "the early rains that blow away the chaff" in the local Shona language - a North Korean-trained brigade rampaged through the southwestern provinces of Matabeleland, leaving 10 000 to 20 000 civilians dead. That's according to a 1997 report by the Catholic Commission on Peace and Justice that drew on more than 1 000 interviews and is seen as the most authoritative account.Like his predecessor, Mnangagwa has refused to apologise but said he will accept recommendations of a national peace and reconciliation commission conducting public hearings on the atrocities.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. "Authorities are not comfortable with this subject," producer Zenzele Ndebele told the screening crowd on Wednesday night."Most people involved in Gukurahundi are now in power. This makes them uncomfortable," said Ndebele, who said he was summoned by police before being allowed to screen the documentary in September in Bulawayo, a city where many of the atrocities occurred.The documentary highlights Mnangagwa's alleged role and features interviews with villagers, former top military officials and politicians narrating how they were tortured and jailed for belonging to an ethnic group accused of harboring anti-government rebels.Some say Mugabe used the military campaign to stamp out support for the rebels. Others saw the massacres as an attempt by Mugabe to weaken any opposition to his stated aim of a one-party state.Villagers recount being kept in camps and forced to dig graves for mass burials. Girls were raped and husbands forced to watch as soldiers raped their wives, witnesses say in the hour-long documentary."Since I was pregnant I was spared," one elderly woman says.Another woman says her husband divorced her because he could not stand sharing her with soldiers.Although the 94-year-old Mugabe now lives quietly in the capital, the atrocities remain a fresh scar. At the screening in Harare, the simmering tensions showed."It was biased, this is vendetta journalism," 26-year-old Lonias Rozvimajoni said afterward. He described witnesses as "bogus" and the documentary as "fiction," to a chorus of support from some. They said the timing of the documentary's release was meant to tarnish Mnangagwa's presidency.Others shouted back, defending the work."You are hired guns," barked Ibbo Mandaza, an academic who runs a non-governmental organisation that hosted the screening, referring to the seemingly pro-government youths."Gukurahundi happened. I was in government at the time, I witnessed it," said Mandaza, who had been a ruling party official.He abruptly ended the session, although the heated exchanges continued over tea and biscuits in the courtyard."Maybe it will take them to become victims to understand," Dumisani Mpofu, who worked on the documentary as a researcher, told The Associated Press.