Nuba on edge ahead of Sudan vote official

The people of the Nuba Mountains, an isolated area in central Sudan, are fearful about what the future may hold for them as the south of the country looks set to gain independence.

They may live in the northern half of the country, but many people here sided with the South in the civil war.

If the South chooses independence, the president is promising sweeping changes to the constitution of the North, including sharia law and enforing Arabic as the official language.

Al Jazeera's Nick Clark reports from the Nuba Mountains, home to a volatile mix of rival Arab and African groups.