South Sudanese government forces and rebels have used hunger as a weapon of war in a region once seen as the country’s breadbasket that’s been ravaged by killings, gang-rapes and looting over the past year, Amnesty International said.

Civilians’ access to food in the southern region of Equatoria, where conflict spread last July, is “severely limited” after combatants cut supplies, looted from markets and homes and targeted civilians, the London-based advocacy group said Tuesday. It said fighters from each side accuse civilians of feeding or being fed by the enemy.

“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,” Joanne Mariner, Amnesty’s senior crisis response adviser, said. Deputy army spokesman Santo Domic said the report hadn’t been shared with the military and was biased.

South Sudan’s civil war has left tens of thousands of people dead and forced more than 3.5 million from their homes since it started in December 2013. Initially much of the fighting was focused in the north, where famine was declared in two counties in January. Though relief efforts mean the areas are no longer designated famine zones, food availability in the country is worsening due to a poor harvest and surging inflation, according to the national statistics office.

‘Grave Abuses’

Rebel groups in Equatoria, a region that had largely been spared the political violence, took up arms last year. Government forces and allied militias have committed “a litany of violations with impunity,” while armed opposition groups have also staged “grave abuses, albeit on a smaller scale,” according to Amnesty, whose researchers visited the area in June. Almost a million people have fled their homes, including to neighboring Uganda, exacerbating what the United Nations has called the world’s fastest-growing refugee crisis.

Much of the violence has centered on the town of Yei, about 150 kilometers (93 miles) south of the capital, Juba, and on a main trade route to Uganda and the Democratic Republic of Congo. Amnesty said eyewitnesses in surrounding villages described how government forces and allied militias “deliberately killed civilians with reckless abandon.”

The attacks on villages by government forces “often appear to be in revenge for the activities of opposition forces in the region,” according to Amnesty. It said rebel fighters also deliberately killed civilians they deemed to be government supporters, often just for being Dinka — the ethnic group to which President Salva Kiir belongs — or refugees from Sudan’s Nuba Mountains accused of sympathizing with Kiir’s administration.

Army spokesman Domic said “the rebel forces are the ones committing atrocities against the civilians because they don’t have a unifying command and control. Left unattended, they can become a security threat to the neighboring countries,” he said by phone from Juba.