Joseph Kony's LRA has spread terror across the region
The UN force in the Democratic Republic of Congo has been accused of doing too little to protect civilians from Ugandan Lord's Resistance Army rebels.
Humanitarian organisation Medecins Sans Frontieres (MSF) said the force was ignoring bloodshed in the north-east of DR Congo, near Sudan's border.
MSF says at least 900 civilians have been stabbed or clubbed to death, and many abducted, including children.
The UN force, known as Monuc, dismissed MSF's claims as "patently untrue".
The LRA have increased their attacks since forces from Uganda, South Sudan and DR Congo launched a three-pronged attack against them in December.
Countries from Uganda to the Central African Republic have suffered 20 years of terror inflicted by the LRA.
Tens of thousands of children have been abducted to be fighters and sex slaves.
'Failed to intervene'
MSF claims that on one occasion, on 1 November, UN peacekeepers stayed in their base while the main town of Dungu came under attack.
The organisation alleges the 17,000-strong UN mission to the region failed to intervene even when the attacks increased, and did not go in to evacuate the wounded.
Unlike aid workers, says MSF, Monuc can reach by helicopter those areas which have recently come under attack.
MSF's Marc Poncin predicted more massacres.
"Monuc must take up its responsibilities and can no longer continue to be so absent for inhabitants when they are being systematically attacked," he said.
MSF said its teams had been shocked by the extreme violence of the LRA in north-eastern DR Congo.
More than 50 villages and towns across Haut-Uele province have been attacked since Christmas Day, according to MSF.
One survivor of an attack near Doruma on Christmas Day told MSF: "No one was spared: Children, infants, pregnant women, the elderly, all killed. More than 60 people."
The BBC's correspondent in the in Congolese capital, Kinshasa, Thomas Fessy, got a response from Monuc.
Its spokesman, Kevin Kennedy, said the force had difficulty monitoring everything that happened in Haut-Uele, an area the size of Belgium.
"MSF knows as well as anyone that Monuc has been extremely active," he said.
"We have been involved in the evacuation of wounded; we have been involved in supporting the delivery of humanitarian aid; we have been doing to the maximum scale possible what Monuc can do under these circumstances."
Attacks on villages in the far north of the DR Congo by the LRA over the last six weeks have driven 130,000 people from their homes.
BBC Africa editor Martin Plaut, in the remote southern Sudanese town of Ezo on the border with DR Congo and the Central African Republic, has seen hundreds of refugees fleeing.
Some walked for up to three days, he says, enduring terrible conditions, taking shelter in huts they made from thatch and straw held together with bamboo.
The LRA insists the International Criminal Court must drop warrants of arrest for its leader Joseph Kony and his top commanders before they can sign a peace deal.
Countries around the region have suffered from 20 years of raids by the LRA.