Amnesty International has accused South Sudanese troops of setting fire to villages and physically abusing civilians in an ongoing military assault on rebels loyal to the country’s former vice-president.

The watchdog reported on Thursday the latest allegations of serious rights abuses since the resumption of heavy fighting last month, as China announced plans to evacuate its nationals working at the Paloch oilfields in the oil-rich Upper Nile state.

“The spike in fighting between the parties to the conflict is a clear indication that South Sudan’s leaders have little interest in a cessation of hostilities,” said Michelle Kagari, a deputy director with Amnesty International.

Citing witness accounts in Unity state, the watchdog group reported Thursday that fighters in South Sudan military uniforms — and others in civilian clothing — have attacked villages using axes, machetes and guns.

“The region and the rest of the international community are reluctant to take bold steps towards addressing repeated atrocities,” she added.

Heavy fighting in the Upper Nile state increased with the rebel forces announcing on Wednesday that they had taken control of most of the Foluj oil field, where workers of the China National Petroleum Corporation are stationed.

The United Nations has expressed concern over the escalation of hostilities in the past few days between the ruling Sudan People’s Liberation Movement (SPLM) and the SPLM in Opposition and their allied forces in Unity and Upper Nile States.

In an announcement made on China’s national television, CCTV, on Thursday, the Chinese embassies in South Sudan and Sudan began evacuating staff of the oil company due to the insecurity around the oilfields as the rebel forces advanced towards them.

“More than 400 Chinese oil workers have been evacuated from South Sudan due to growing violence,” said the statement by the Chinese government. Beijing said the evacuated oil workers will be flown home in the coming few days.

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The UN Office for the Co-ordination of Humanitarian Affairs (OCHA), says some 100,000 people have been displaced by the recent fighting in Unity State.

About 2,300 civilians, mostly women and children have sought refuge at the UN base in Bentiu since April 20, joining over 50,000 others who have fled to refuge at the camp since the start of the conflict in December 2013.

Government forces have blocked other internally displaced people at checkpoints, preventing them from reaching the safety of the UN base. Thousands have fled into the bush or swamp areas.

Ariane Quentier, the spokesperson for United Nations Mission in South Sudan (UNMISS), says he was appalled by the reports of human-rights violations “committed by the SPLA and their allied forces, including the burning of villages, and the killing and rape of civilians, in the course of their military operations in Unity State.”

The UN Office of the High Commissioner on Human Rights (OHCHR) reported that at least 28 towns and villages in Unity State were attacked between April 29 and May 12. Civilians were targeted and their property was looted.

“These attacks on civilians in Unity State, and the ensuing displacement, mirror events documented by Amnesty International in early 2014,” said Ms Kagari.

“The fact that some of the same villages and towns are being subjected to a repeat round of atrocities underlines the need for the African Union, the UN and other international bodies to match their tough rhetoric with concrete action to reduce the human costs of the conflict.”

The UN demands that immediate national investigations be conducted so that those responsible for these crimes are held accountable, adding that the fighting is “unacceptable” because “it is part of a series of violations of the Cessation of Hostilities Agreement signed by the parties on January 23, 2014.”

Additional reporting by AFP