Fighting in the tense boundary region between northern and southern Sudan has killed at least 25 people.
Officials say fighters from the Misseriya, a tribe of Arab nomads, clashed with the former southern Sudanese rebel group, the Sudan People's Liberation Army (or SPLA).
Details are sketchy, but Misseriya leaders say their fighters launched an attack Saturday in retaliation for an attack by the SPLA last week. At least one person was killed in that earlier clash.
Tension has increased in the region as Sudan's northern-based ruling party and the former southern rebels argue over the boundaries of the oil-rich Abyei area. The Sudanese government is believed to support the Misseriya.
Abyei's status was left unresolved in the peace deal that ended 21 years of civil war between the north and the south in 2005.
Under that agreement, southern Sudan gained general autonomy and is scheduled to hold a referendum on secession in 2011.
The deal calls for nothern and southern Sudan to divide oil wealth equally but the north has refused to give up parts of Abyei.
In October, southern ministers temporarily withdrew from Sudan's national government to protest what they called the north's refusal to carry out the 2005 peace deal.
Analysts from the International Crisis Group have warned the Abyei dispute may cause the peace deal to disintegrate.