Rebel fighters in the Democratic Republic of Congo have threatened to march on the capital, Kinshasa, after capturing the eastern city of Goma.
The M23 rebel commander told a crowd in Goma they were ready to topple President Joseph Kabila.
The rebels have also taken a small town near Goma, which is on the road to the region’s other main city, Bukavu.
Meanwhile, Mr Kabila is holding crisis talks with his Rwanda and Ugandan counterparts.
In a joint statement, the three – Mr Kabila, President Paul Kagame of Rwanda and President Yoweri Museveni of Uganda – called on the M23 to “immediately stop [its] offensive and pull out of Goma”.
In Bukavu, the city about 230km (143 miles) south of Goma which the rebels say they also intend to capture, there have been protests about the government’s – and the UN’s – perceived military failings.
The rebel threat has renewed fears that the 1997-2003 war in DR Congo, during which some five million people died, could reignite.
Last month, a UN panel of experts accused Uganda and Rwanda, both neighbours of DR Congo, which is the size of western Europe, of backing the M23 rebel group.
When the rebels entered Goma on Tuesday, they apparently faced little resistance from government and UN troops.
On Wednesday the UN defended its actions in preceding days, saying it had fired hundreds of rockets at the rebels in an effort to block their advance on Goma, the main city in eastern DR Congo with a population of about a million.
In Goma, M23 spokesman Lt Col Vianney Kazarama addressed a crowd at a football stadium in the city.
“Do you want us to march to Kinshasa?” he said, and the crowd shouted back: “Yes!”
The M23 rebel group, which was formed in April following an army mutiny, said it had added 2,000 fighters to its ranks from former Congolese soldiers who came to the stadium, as well as 700 policemen.
Lt Col Kazarama said that “the journey to liberate [DR] Congo has started now”.
He said they were “going to move on to Bukavu and then to Kinshasa”, which is about 1,600km from Goma.
Simone Schlindwein, a reporter for the German newspaper TAZ, who is now in Sake – the town 27km outside Goma which has also fallen to the rebels – says she saw the bodies of several Congolese soldiers on the way there, an abandoned tank and bombs and grenades lying around.
In Bukavu, the offices of the ruling party have been burnt down by protesters angered by the government’s and UN’s inability to protect them.
Jean-Christophe Pegon, of the European Commission’s humanitarian department (Echo) based in Bukavu, told the BBC’s Focus on Africa programme it reached a point when “police forces had to use live ammunition against demonstrators” to disperse them.
“It was both against the M23 and the regime of Kabila – it seems they were parading with a dead dog wearing the hat of the ruling party and chanting: ‘Dead dog Kabila’,” Mr Pegon said.
The UN, which has about 19,000 troops in DR Congo, says it has received reports that the rebels have abducted women and children from Goma. Killings and looting have also been reported.
The UN Security Council has adopted unanimously a resolution condemning the rebel seizure of Goma and calling for sanctions against M23 leaders.
In its resolution, the Security Council demanded an end to foreign support – seen as a reference to Rwanda and Uganda – for the rebels.
However, both countries have denied that they are arming the rebels whose rebellion has displaced some 500,000 people since April.
President Kabila has urged the Congolese nation to “resist” the rebels and said “war had been imposed” on the country.
President Kabila took power following the assassination of his father, Laurent, in 2007.
About a decade earlier, Laurent Kabila had taken power in Kinshasa after marching from the east with rebel forces backed by Rwanda and Uganda.
Mr Kabila later fell out with his regional allies.