Residents of the contested Abyei region have gone to polls in an unofficial referendum to decide whether they belong to Sudan or South Sudan.

The referendum lacks the official backing of the governments in Khartum and Juba.

The referendum, organized by a civic group, will last three days and its results will be made public on Thursday.

“The people are voting to choose to join South Sudan or to be part of Sudan,” said Rou Manyiel, chairman of the Abyei civil society organization.

Up to 100,000 people are expected to take part in the referendum.

“There are long queues of people, but things are peaceful and calm,” Manyiel stated.

“They began to vote on Sunday and they will finish voting on Tuesday, the third day.”

The vote is expected to inflame tensions as Khartoum and Juba both claim sovereignty over the flashpoint oil-rich region.

The United Nations and the African Union have already warned about any such unilateral move, saying it could undermine the fragile peace in the region.

The status of Abyei remained unresolved after South Sudan became independent from its northern neighbor in 2011.

Last week, Sudanese President Omar al-Bashir held talks with his southern counterpart Salva Kiir to settle the future of Abyei, but the meeting ended inconclusively.