The commander of the M23 rebel group in the eastern Democratic Republic of Congo has surrendered in Uganda, sources have told the BBC.
Sultani Makenga is said to have handed himself over along with hundreds of M23 fighters in the Mgahinga National Park.
A Ugandan spokesman said no decision had yet been made on whether he would be handed over to DR Congo.
Earlier this week the M23 said it was ending its insurgency, hours after the DR Congo government claimed victory.
Reports say Col Makenga and about 1,700 fighters have been disarmed and are being held in a secret location.
The BBC's Catherine Byaruhanga in Kampala says Col Makenga poses a tough diplomatic challenge for Uganda.
He is wanted back home for war crimes for his leadership of the rebellion and is also under UN sanctions.
A Ugandan government spokesperson told the BBC a decision on whether to hand him over would have to wait until a peace deal is signed between DR Congo and the M23 rebels, which is expected this weekend.
Both DR Congo and the UN are adamant that the M23's top commanders will not be given amnesty, our correspondent says.
Uganda has been hosting peace talks between the rebels and the DR Congo government.
The M23 has wrought havoc across eastern DR Congo since it began its insurgency in April 2012.
Its fighters are mostly from the Tutsi ethnic group, a minority in eastern DR Congo but with ties to Rwanda's leaders.
Their name refers to a 23 March 2009 peace deal which a former militia group - the CNDP - signed with the Congolese government. The rebels said the government had not lived up to its promises in the deal.
Analysts say the surrender of Col Makenga, if confirmed, will be a major success for the Congolese army which has been struggling to restore calm in eastern DR Congo for two decades.
Earlier this year the UN approved a new mission of 3,000 African soldiers with a mandate to fight the rebels.
They have the operational support of the existing UN Mission in DR Congo (Monusco) and have used helicopters to target the rebels, allowing the army to advance.
Both Rwanda and Uganda have denied UN allegations that they supported the M23.