Both the Ugandan army and the rebel Lord's Resistance Army have violated the terms of their truce, a report on the Ugandan peace process says.
Both the army and the LRA have admitted violating the agreement
In August, the two sides agreed a deal aimed at ending two decades of conflict in Uganda at peace talks in Sudan.
LRA rebels pledged to assemble at two points in southern Sudan by mid-September in return for an amnesty. But rebels had left one of the points, while the army had approached a rebel safe haven, a monitoring team found.
Both sides admitted the violations.
"We are sorry that we breached the cessation of hostilities agreement," said Ugandan Deputy Defence Minister Ruth Nankabirwa.
"They (the army) wanted to ascertain whether LRA rebels were assembling," she said, urging the rebels to return to the designated areas.
A spokesmen for the LRA, Godfrey Ayo, said rebels left their assembly point in violation of the agreement because they feared an attack.
The allegations on both sides demonstrate the mistrust between the Ugandan government and the LRA rebels, says the BBC's Sarah Grainger in Kampala.
The two sides have been fighting for nearly 20 years. Tens of thousands of people have been killed and more than one million people have been forced from their homes.