The Congolese army has been driven back by Gen Nkunda's rebels
Army troops have been looting and targeting civilians in villages in eastern Democratic Republic of Congo, a UN spokesman has said.
UN spokesman Lt-Col Jean Paul Dietrich said the looting around Kanyabayonga began in the early afternoon on Monday and continued through the night.
There were reports of women being raped during the looting, he said.
Troops in eastern DR Congo have been battling rebels loyal to a renegade general, Laurent Nkunda.
More than 250,000 people have been displaced by the violence, triggering a major humanitarian crisis.
On Tuesday, Gen Nkunda swore in an alternative administration for the east of the country where his forces had made recent gains, in what observers say is his latest direct challenge to the central government.
Twelve ministers will take responsibility for a range of functions including police and security.
However, a BBC correspondent in eastern DR Congo says the move appears to be pure propaganda.
Our correspondent says it may annoy the government but is likely to be insignificant unless General Nkunda follows it up with further military action.
'Aid workers trapped'
Lt-Col Dietrich told the BBC that the villages that were targeted in the Kanyabayonga area were controlled by the government, but the looting may have been sparked by rumours of a rebel attack.
He said UN peacekeepers and the Congolese army had been trying to stop the looting.
"I think that things are now getting under control," he said.
A spokesman for the UN humanitarian affairs agency was quoted as saying some aid officials had been trapped by the latest violence and the UN force was trying to bring them to safety.
Recent fighting has hampered aid efforts. Tens of thousands of displaced people are in camps north of Goma, some exposed to diseases including cholera.
Aid officials say many people remain in urgent need of food, clean water, healthcare and shelter.
Gen Nkunda claims to be fighting to protect his Tutsi community from attacks by Rwandan Hutu rebels, who fled to DR Congo after Rwanda's 1994 genocide.
On Monday, he threatened to take over the whole country if President Joseph Kabila's government continued in its refusal to negotiate with him.
But a Congolese official said the government was still unwilling to talk to the rebel leader and accused him of war crimes.
The UN has accused both sides of war crimes during the latest violence, following the reported killing of civilians in the eastern town of Kiwanja last week.
In recent weeks, Gen Nkunda's forces have taken a series of towns and villages near Goma, the capital of DR Congo's North Kivu province.
FORCES AROUND GOMA
CNDP: Gen Nkunda's Tutsi rebels - 6,000 fighters
FDLR: Rwandan Hutus - 6,000-7,000
Mai Mai: pro-government militia - 3,500
Monuc: UN peacekeepers - 1,000 in Goma, 6,000 in North Kivu (17,000 nationwide)
DRC army - 90,000 (nationwide)
Source: UN, military experts
Gen Nkunda said on Monday that he was still observing a ceasefire declared late last month, and that since then he had only been responding to attacks by pro-government militia.
Mr Kabila was elected president in 2006 in polls that were backed by the UN, and which international observers generally declared to be fair.
As in the five-year war that began in DR Congo in 1998, the recent fighting has threatened to draw in neighbouring countries.
This weekend, southern African countries expressed their support for Congolese government forces and said they were sending military advisers and experts to the country.
Rwanda has long been accused of - and denied - supporting Gen Nkunda's forces.
It has twice invaded DR Congo, saying it wanted to act against the Hutu rebels.