A ceasefire between Uganda's government and the Lord's Resistance Army rebels has come into force.
LRA fighters are to assemble in southern Sudan
The truce, signed on Saturday, gives rebels three weeks to assemble at points in southern Sudan where the regional government will protect them.
Comprehensive peace talks are then meant to start. Uganda has pledged that it will not try to attack the rebels.
Thousands have died during the 20-year conflict in northern Uganda, and more than one million have fled their homes.
The ceasefire took effect at 0600 local time (0300 GMT) on Tuesday.
Ugandan army spokesman Maj Felix Kulayigye told the BBC that so far the truce was holding.
The UN's most senior humanitarian official, Jan Egeland, welcomed the ceasefire, describing the situation in northern Uganda as "the world's worst neglected emergency".
LRA leader Joseph Kony is wanted by the ICC for war crimes
"Now, with the assistance of the Government of South Sudan, we have a real chance to make progress," said Mr Egeland, the UN under secretary general for humanitarian affairs.
Humanitarian organisations say they are ready to assist the women and children who were captured by the LRA and forced into marriage or used as slaves or soldiers, and who are to be released in compliance with the ceasefire deal.
"We are standing by to help ensure the safe and smooth release and return of women and children who have been separated from their communities for so long," Chulho Hyun, Uganda spokesman for the UN children's agency Unicef told Reuters news agency.
Those LRA soldiers who are currently in Uganda are to proceed to Sudan.
Ugandan Army spokesman Major Felix Kulayigye said there was only a "small group" of LRA fighters on Ugandan soil.
More than 1m Ugandans have fled their homes
"We have estimates, not exact numbers, but in northern Uganda we have not more than 100," he told the BBC's Focus on Africa programme.
"We trust the LRA will meet their side of the bargain and assemble everybody," Maj Kulayigye said.
"Their safe passage will be honoured by the UPDF (Ugandan People's Defence Force)," he said.
LRA soldiers stationed in DR Congo have already begun leaving their bases, from where they are meant to go to the assembly points in Sudan.
Meanwhile, rebel leader Joseph Kony and his senior commanders are gathering on Congolese territory near the border of the Central African Republic.
Diplomats say the plan is to fly them to the assembly points in Sudan.
Jessica Nkuhe, a member of a women's organisation in northern Uganda, said it was too early to celebrate.
"We are hoping it will hold. Many times we have had false starts - we hope both sides have the seriousness it takes to hold the truce and then negotiate in earnest," she told the BBC's Network Africa programme.
LRA spokesman Obonyo Olweny insisted "the validity of the agreement depends on the Ugandan government adhering," but said he was optimistic the agreement would hold even if not all troops were quartered by the 12 September deadline.
"If there is not enough time it will be reviewed and an extension will be made to cover the movement of troops," he told the BBC.
The International Criminal Court (ICC) wants the LRA's top officials - among them Joseph Kony - to face charges including murder, rape and forcibly enlisting children. The LRA has abducted thousands of children and forced them to fight since the conflict began.
Against the wishes of the ICC, Uganda offered amnesty to LRA leaders in exchange for the peace talks.