The Ugandan army has accused Lord's Resistance Army rebels of violating a truce by deserting a neutral camp in southern Sudan.
A Ugandan army spokesman told reporters Tuesday that rebels who had gathered at the Owiny-Ki-Bul camp have departed, along with a top commander.
The spokesman says the army will take action to keep the rebel fighters from regrouping.
Hundreds of rebels had assembled at the camp in recent weeks under terms of a truce agreement the rebels reached with the Ugandan government.
Peace talks in southern Sudan are aimed at ending the rebels' 20-year insurgency.
The talks have been clouded by several issues, including a refusal by the International Criminal Court to drop war crimes charges against five top LRA leaders.
LRA fighters are accused of killing, kidnapping and mutilating thousands of civilians during their long uprising.
Earlier this week, rebel delegates to the talks demanded that the Ugandan government replaced its lead negotiatior. But Wednesday, a Ugandan newspaper quoted the rebels' second in command, Vincent Otti, as saying he has no problem with government negotiator Ruhakana Rugunda.
Otti and top rebel leader Joseph Kony are not attending the talks, citing fears of arrest on war crimes charges.
Some information for this report was provided by AFP and AP.