|South Kordofan is a focus of growing military tension between north and south Sudan ahead of the January 9 vote
Armed men from the Sudanese Messiria tribe have taken almost 1,000 people hostage in a tribal feud over blood money.
The hostages were travelling from Khartoum, the capital, to the South, to vote in the January 9 referendum that is expected to lead to the breakup of Africa's largest nation when they were seized.
The Messiria tribesmen stopped their convoy of about 150 cars in the northern state of South Kordofan.
They said they plan to hold the hostages until the government of the South Sudan's Unity State pays a retribution for the killing of several Messiria shepherds earlier this year.
Al Jazeera's Mohamed Vall, reporting from Khartoum, said that the government of South Sudan has denied any involvement in the hostage situation.
"It started several months ago when elements of the southern tribes in Unity State attacked the Messiria, took some of their cars and killed three of their shepherds," he said.
"A settlement was reached between the two sides whereby Unity State should pay blood money to the Messiria. Now, the Messiria are saying they have been waiting for that payment for a long time and they decided to take action to put pressure on Unity State."
The government of South Sudan said that negotiations are ongoing and that a solution might be reached soon.
The Messiria belong to the Baggara Arabs tribes and speak Sudanese Arabic. Numbering over one million, the Baggara are the second largest ethnic group in Western Sudan, extending into Eastern Chad.
They are primarily nomadic cattle herders and their journeys are dependent upon the seasons of the year.
South Kordofan is a focus of growing military tension between north Sudan and the neighbouring region of southern Sudan which is weeks away from the scheduled start of a referendum on whether it should secede.