Aerial view showing fire at the village of Abyei, Sudan (File)

A leading human rights group says tens of thousands of civilians are unable to return to their homes in the Sudanese town Abyei.

Human Rights Watch says fighting between forces of Sudan's northern-based government and the semi-autonomous south displaced tens of thousands of Abyei residents in May. But the the New York-based group says many of those residents cannot return for fear the violence could erupt again.

It accused the Sudanese Armed Forces of restricting access to the disputed town in the weeks after the clashes, and blocking a full and independent investigation into the violence.

The rights group says there is still no clear information on how many civilians died in the fighting.

Human Rights Watch also says the Sudanese Armed Forces and allied militia are responsible for widespread looting, burning and destruction in Abyei.

The town sits at the center of the oil-rich Abyei region, claimed by both the southern administration and the northern-based national government.

A 2005 peace deal ended 21 years of war between northern and southern Sudan.

As part of the deal, southern Sudan is scheduled to hold a referendum in 2011 over whether to secede from the rest of the country.

Some information for this report was provided by AP.