Senior military sources say rebels in the Democratic Republic of Congo have captured a second strategic town in the east of the country.
Gen Nkunda denies he is a mutineer
Reports say renegade fighters have gained control Walikale, 150km (93 miles) west of Bukavu, which rebels seized on Wednesday.
The United Nations has confirmed that the fighting has spread.
Renegade Gen Laurent Nkunda has denied that his troops were moving towards other towns.
Gen Nkunda said he had withdrawn all troops except those protecting key installations and his senior officers. The troops were moving to barracks outside Bukavu, he said.
He said he would withdraw his remaining officers and their bodyguards from Bukavu on Sunday.
Under a deal struck by the UN, rebel fighters had pledged to withdraw from the town by Friday evening.
The soldiers are members of a former rebel group, the RCD, that is supposed to be integrated into Congo's new national army.
In Walikale, there were clashes between two factions of the army on Friday and one of the factions were forced out, leaving the former RCD.
A UN spokesperson said that if it was confirmed that the soldiers were siding with Gen Nkunda, it would be signal a serious threat to peace in the area.
"This is very disturbing," said Hamadoun Toure from the capital Kinshasa.
"After Walikale there's Kisangani. This is something that would be very dangerous for the peace process and for the region."
The recent fighting in Bukavu has sparked fears that DR Congo's fragile peace process may be unravelling.
Gen Nkunda has said: "I'm not a mutineer because I'm not fighting the government. I just came to kick out troops... who were killing a section of the Congolese community."
Renegade commanders - who are ethnic Banyamulenge, related to Rwandan Tutsis - say government forces have been attacking members of their community.
Is this the end of peace in DR Congo? Should the UN have stopped the rebel advance?
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