Nairobi - South Sudanese government troops crushed fleeing civilians with tanks, then reversed to check they had killed them, carried out public gang rapes and burned people alive, a rights group said on Wednesday.
The report by Human Rights Watch (HRW) has shocking allegations of atrocities committed by government forces in the ongoing 19-month-old war, documenting "deliberate attacks on civilians" that it said constitute war crimes.
"They were running with the tanks after the people, and then after they hit them they would roll back over them, to confirm that they were dead," one woman told HRW.
Attacks were carried out by government troops and an allied militia from the Bul Nuer tribe.
Another witness, a 30-year-old woman, said troops in a tank hunted down her nephew.
"I saw him... he was crushed before he reached the river... we were running together, he ran in order to hide," she told HRW.
Another described finding the squashed bodies of her two male relatives.
"Their bodies had been grinded," she said, one of a string of testimonies documented in the HRW report, titled "They Burned it All", based on interviews with 174 victims and witnesses from the northern battleground state of Unity.
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Other victims recount government soldiers castrating a man and a 15-year old boy, all part of a deliberate tactic to drive people out of the villages, HRW said.
HRW documented murders "of civilian women and men, including children and the elderly, some by hanging others by shooting, or being burned alive."
The civil war began in December 2013 when President Salva Kiir accused his former deputy Riek Machar of planning a coup, setting off a cycle of retaliatory killings that has split the poverty-stricken, landlocked country along ethnic lines.
The government side, the Sudan People's Liberation Army (SPLA), launched a major offensive against rebel forces in April, with fierce fighting in Unity, once a key oil producing area.
Rebel forces have also been accused of carrying out atrocities, including rape, killings and, like the government, the recruitment of armies of child soldiers.
There was no immediate response from the army, which has previously dismissed allegations of rights abuses.
Earlier this month the government said it was investigating the UN reports that troops raped then burned girls alive, but has not yet issued its findings.