Four African heads of state have begun a summit to try to resolve the crisis in the Democratic Republic of Congo.
The talks are being held in Uganda, which alongside Rwanda, has been accused of backing M23 rebels who took the eastern city of Goma on Tuesday. Both countries deny the charges.
The UN has warned of a humanitarian crisis with food and medicines running short.
Armed groups have battled over mineral-rich eastern DR Congo for two decades.
About 500,000 people have been displaced by the rebellion since it began in April, with the formation of the M23 rebel group after a mutiny in the army.
The rebels said they were not given army posts promised in a 2009 deal to end a previous uprising.
Their exact aims are unclear but they have also advanced beyond Goma, the biggest city in eastern DR Congo, taking the town of Sake despite a loyalist fight-back.
They have threatened to attack the capital, Kinshasa, if President Joseph Kabila does not open negotiations with them.
Rebels at the talks?
President Kabila and the presidents of Uganda, Kenya and Tanzania are attending the Uganda talks but the Rwanda leader, Paul Kagame, has stayed away. He is represented by his foreign minister.
A BBC correspondent at the summit says some of the M23 leaders are also in Kampala.
The meeting was said to be discussing a possible pledge by Mr Kabila to listen to the rebels' grievances, in return for their withdrawal from Goma and an end to their threat to topple the elected government.
So far, the rebels have rejected a call by regional leaders to withdraw from the main eastern city of Goma, capital of North Kivu province.
On Thursday, the head of DR Congo's army was suspended pending an investigation into claims that he sold weapons to rebel groups.
A UN report accused Gen Gabriel Amisi of running a network supplying arms to poachers and rebel groups including the notorious Mai Mai Raia Mutomboki.
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The UN has accused Rwanda and Uganda of backing the M23, saying the chain of command culminates with Rwandan Defence Minister James Kabarebe.
The M23's gains have raised fears of renewed war in DR Congo, where some five million people died in a conflict from 1997-2003.
The UN Security Council has adopted a resolution condemning the rebel seizure of Goma and calling for sanctions against M23 leaders.
Tens of thousands of civilians have fled as the rebel forces have advanced, scattering from villages and refugee camps.
The United Nations' children's fund Unicef says hundreds of children have been separated from their parents. It warns that many of them risk being recruited by armed groups.
United Nations refugee agency spokesman Adrian Edwards said: "UNHCR is extremely concerned about the situation of displaced people in North Kivu in particular, especially children and other vulnerable groups.
- BBC