Meanwhile, the leader of the rebel group known as M23 headed to neighboring Uganda where emergency talks were held this week between the presidents of Congo and its neighbors Uganda and Rwanda.
Fighting broke out Thursday just before noon in the town of Sake, which the rebels had seized Wednesday after capturing the strategic provincial capital of Goma, about 17 miles (27 kilometers) away.
One woman whose husband had died of mortar shrapnel to the head wailed as she was carried by her relatives out of town.
Rebel spokesman Lt. Col. Vianney Kazarama vowed Thursday that the fighters would press forward toward seizing the strategic eastern town of Bukavu, which would mark the biggest gain in rebel territory in nearly a decade if it were to fall.
The presidents from Congo, Rwanda and Uganda who met in the Ugandan capital of Kampala have called on the fighters to give up the territory they now control. Congolese President Joseph Kabila later said he was willing to talk with rebel representatives.
"We are not stopping at all; the determination is the same. Whatever happens in Kampala does not affect us," Kazarama told The Associated Press, confirming that rebel leader Col. Sultani Makenga was traveling to Uganda.
There are fears that the rebels' advance could spark a new regional war in a highly volatile corner of the world. Already the violence in eastern Congo has forced more than 100,000 people to flee, more than half of whom are children, according to the U.N. children's agency.
While the rebels have vowed to overthrow Kabila's government, they remain some 1,000 miles (1,600 kilometers) from the capital, Kinshasa, in a country of dense jungle with few paved roads.
Rwanda, and to a lesser extent Uganda, have been accused of backing the rebels and of equipping them with sophisticated arms, including night vision goggles and 120 mm mortars. It is widely believed that Rwanda is interested in eastern Congo's minerals.
A report released Wednesday by the U.N. Group of Experts said both Rwanda and Uganda have "cooperated to support the creation and expansion of the political branch of M23 and have consistently advocated on behalf of the rebels."
The report's release, just one day after the violent takeover of Goma, is sure to increase pressure on the international community to confront the two eastern African countries over their role in neighboring Congo's conflict.
Both Rwanda and Uganda have repeatedly denied supporting the M23 movement and have faced little international criticism over the allegations.
The three presidents said in a joint statement released at the end of their talks in Kampala that they resolved to force M23 rebels to give up Goma and make a retreat.
"Even if there are legitimate grievances by the mutineering group known as M23, (the presidents) cannot accept the expansion of this war or entertain the idea of overthrowing the legitimate government of (Congo) or undermining its authority," the presidents' statement said.
Goma was last threatened by rebels in 2008 when fighters from the now-defunct National Congress for the Defense of the People, or CNDP, stopped just short of the city.
Their backs to the wall, the Congolese government agreed to enter into talks with the CNDP and a year later, on March 23, 2009, a peace deal was negotiated calling for the CNDP to put down their arms in return for being integrated into the national army.
The peace deal fell apart this April, when up to 700 soldiers, most of them ex-CNDP members, defected from the army, claiming that the Congolese government had failed to uphold their end of the deal.
(Copyright 2012 by The Associated Press. All Rights Reserved.)