The government of South Sudan and its militias are behaving with vicious brutality in the country, with reports of men being locked in huts and burned to death, and of machete attacks being carried out in remote villages.

The atrocities are just one of the causes of the major refugee crisis in the region, with almost a million people fleeing to Uganda. Out of a population of some 12.5 million, more than 1.7 million are enduring severe hunger, classified as just one step below famine, and the number at risk of starvation is 6 million and growing. On top of that, a fast-spreading cholera outbreak threatens to kill thousands. The human rights group Amnesty International, which has been gathering together reports from the conflict, said forces – those loyal to the government and also some to the opposition – had also cut food supplies to parts of the country.

Women and girls are increasingly being abducted and raped in the region of Equatoria, a new frontline in the conflict, which is now a region of “treacherous killing fields”, according to Amnesty.

“The escalation of fighting in the Equatoria region has led to increased brutality against civilians. Men, women and children have been shot, hacked to death with machetes and burned alive in their homes. Women and girls have been gang-raped and abducted,” said Donatella Rovera, Amnesty International’s senior crisis response adviser.

Joanne Mariner, another crisis response adviser for Amnesty, said: “It is a cruel tragedy of this war that South Sudan’s breadbasket – a region that a year ago could feed millions – has turned into treacherous killing fields that have forced close to a million to flee in search of safety.”

After more than half a century of struggle, South Sudan gained independence from Sudan in 2011. The celebrations that marked the birth of the world’s newest country were emotional, but two years later, a falling-out between the country’s president, Salva Kiir, and his then vice-president, Riek Machar, sparked new conflict. Kiir is Dinka and Machar Nuer, two dominant ethnic groups in South Sudan that have been rivals for more than a century, and although Machar, now leader of the opposition, fled the country after a peace deal collapsed last year, troops loyal to him continue to fight the government.

The only way for women and girls to be safe is to be dead Mary, 23, rape survivor

The report describes one incident in May, in which six men were killed: soldiers forced them into a hut in Kudupi village near the Ugandan border and set it on fire, then fired shots into it. The troops shot four of the men as they tried to flee. Another six were killed in a similar attack in Payawa village two days later, which one of their widows said was “the fifth time the village was attacked by the army”. On previous occasions, she said, they would rape, torture and loot, but not kill. Eyewitnesses described seeing government soldiers carry out many such killings.

“All parties to the conflict must rein in their fighters and immediately cease targeting civilians, who are protected under the laws of war,” said Mariner. “Those on all sides responsible for atrocities must be brought to justice. Meanwhile, UN peacekeepers must live up to their mandate to protect civilians from this ongoing onslaught.”

East African leaders said last month they would try to push for peace talks to be revived and to delay next year’s scheduled elections.

“There is no way to be safe so long as we are alive, this is how bad it is,” one 23-year-old rape survivor, Mary, told the human rights group. “The only way for women and girls to be safe is to be dead.”