Vote counting began Wednesday on a unilateral measure to determine whether Sudan or South Sudan would control the disputed border region.
The African Union said it considered the vote illegal. Deng Alor, director of an Abyei referendum committee, told the independent Sudan Tribune there was no other choice.
"The people of Abyei have been forced to conduct their own referendum as a result of inaction by the African Union Peace and Security Council to implement the ... proposal on the final status of Abyei," he said in an interview published Tuesday.
The status of Abyei was to be determined during a 2011 referendum that led to the creation of an independent South Sudan. The new country was established as part of a comprehensive peace agreement that ended Sudan's civil war in 2005.
The 2011 measure was delayed because negotiators couldn't agree on who was eligible to take part in the referendum.
Only one of the two tribes in the region, Ngok Dinka, took part in the referendum. The Arab Misseriya tribe, which is allied more closely with the Khartoum government, boycotted the vote.