Fighters from the Democratic Republic of Congo's M23 group, including their commander Sultani Makenga, have surrendered in Uganda, officers have said, signalling the end of an 18-month armed conflict.
The rebel surrender follows a crushing defeat at the hands of the UN-backed Congolese armed forces.
"He is with our forces, yes, Makenga has crossed into Uganda," a senior Ugandan military officer told AFP news agency, although he declined to clarify if he had formally surrendered or was under arrest.
Paddy Ankunda, a colonel in the Ugandan army, told AFP news agency on Thursday that 1,500 men from the M23 - a number thought to account for almost the entire force - had crossed into Uganda and given themselves up, and were now being held in the Kisoro border district.
"About 1,500 fighters surrendered today," said Ankunda, the spokesman for the Ugandan defence minister Crispus Kiyonga, a mediator in stalled peace talks between M23 and Kinshasa.
However, Ankunda said he was "not aware" if Makenga was among those to have surrendered.
Uganda has been accused by United Nations experts of backing the M23. Those claims are strongly denied by Kampala.
The rebels' surrender puts paid to fears that they might try to fight on despite having been outweighed by superior firepower, notably helicopter gunships.
Makenga, 39, a former colonel in the DR Congo army, is accused of masterminding killings, abductions, using rape as a weapon of war and recruiting child soldiers, and is on both UN and US sanctions lists.
His prescence in Uganda, arrested or not, poses a diplomatic headache for Kampala.
Congolese troops backed by a special UN intervention brigade with an offensive mandate launched a major assault late last month against the M23 force of army mutineers in turbulent North Kivu.
After briefly seizing the regional capital and mining hub of Goma last November, the M23 entered into fresh peace talks which fell apart last month, leading the Congolese army to go on the attack in a bid to end the rebellion.
Makenga was born to parents from the Masisi area north of Goma, but grew up in the neighbouring Rutshuru district.
Like many of the ethnic Tutsi officers who fought alongside him, he cut his teeth in the ranks of the Rwandan Patriotic Front, now in power in neighbouring Rwanda, when it launched a rebellion in the early 1990s.
He then served as a battalion commander in the Rwandan-backed Congolese Rally for Democracy before joining former DRC rebel leader Laurent Nkunda's National Congress for the Defence of the People.
Ever since he has been seen as loyal to Nkunda, who has spent the past several years under house arrest in Rwanda after he fell out with his former mentors in Kigali.
The US also indicated on Wednesday that it was ready to lift sanctions on Rwanda, imposed last month, if Kigali cuts ties with Congolese M23 rebels.