UN Peacekeepers patrol Abyei Reuters

Tens of thousands of civilians stranded in makeshift refugee camps in South Sudan need more support from the United Nations to return home, a charity has claimed.

Amnesty International is calling on the UN to step up its security efforts to help more than 100,000 people who were displaced from the contested north-south border region of Abyei in May when President Omar al-Bashir sent tanks and troops into the area.

Civilians wanting to return home face threats from the army, militias and landmines and are dependent on humanitarian aid for shelter, food and healthcare, the charity said.

"The Sudanese army and allied militia have driven virtually the entire population out of Abyei and burned down their homes so as to prevent their return," said Donatella Rovera, Amnesty International's senior crisis response adviser.

She visited Abyei in November and described it as a ghost town of charred homes and the shells of looted buildings.

"Everything of value has been looted, including humanitarian organisations' facilities, and now the only signs of life are the soldiers and UN peacekeepers," she said.

She called for the UN to carry out a thorough investigation into the events in May, which al-Bashir blamed on southern troops attacking convoys, and to release any information it has gathered so far.

"We have hardly any food and nothing else," said Angeline Aguir, a mother of two who is sheltering in a camp in the village of Mayen Abun.

"I don't know what has happened to our home. We cannot go back so long as the army is there."

The Un Mission in the Sudan (UNMIS) was criticised for a lack of decisive action during the attacks on Abyei. A new peacekeeping force, the United Nations Interim Security Force for Abyei (UNISFA) has a mandate to protect civilians.

"The first step is to create the necessary security conditions in Abyei for the safe return of the population and to put in place robust mechanisms to implement the protection of civilians and human rights monitoring aspects of UNISFA's mandate," Rovera added.

Both Sudan and South Sudan claim Abyei as part of their territory. A referendum on the future of the area has been indefinitely delayed because of arguments over voter eligibility.