A dissident Congolese army officer says there is a state of war between the government and his forces in the east of the Democratic Republic of Congo.
Laurent Nkunda says he cannot accept an order to lay down arms
Speaking to the BBC, General Laurent Nkunda, a Congolese Tutsi, accused the government of forming an alliance with Hutus to attack his troops.
Heavy fighting is reported in the Kivu region, with the Congolese army moving troops into the area.
The UN refugee agency says tens of thousands have fled from their homes.
The UNHCR says people are afraid of being caught between government forces, former Rwandan rebels and troops of General Nkunda.
General Nkunda told the BBC his forces had handed over Rwandan Hutu FDLR rebels to the UN peacekeeping mission, known as Monuc.
"For me it's a state of war... we have prisoners of war from the FDLR who were attacking with the government troops," he said.
He said he could not support a government that was working with Hutus and would not accept an order to disarm his forces.
The BBC's Africa analyst, Martin Plaut, says that the government and the general are now well armed and supplied and an uneasy standoff is currently in place.
DR Congo Defence Minister Tshikez Djemu said that if soldiers allied to General Nkunda refused to lay down their arms, they would be considered bandits and be dealt with accordingly by the army.
Tension is nothing new to North Kivu but it has suddenly increased after the government's decision to dismantle what are known as the mixed brigades, our correspondent says.
These brigades, created earlier this year, were made up of government soldiers and more than 7,000 former rebels.
They joined the brigades on condition that they would remain deployed as a group to protect their own community, the Tutsis, against Rwandan Hutu rebels, some of whom took part in the 1994 genocide of Tutsis.
But since the beginning of this year, military operations launched by the mixed brigades against the Hutu rebels have created more instability and the UN says more than 170,000 civilians have been displaced.