Kinshasa, DR Congo - Uganda's rebel Lord's Resistance Army has reportedly torched a church crowded with worshippers holding a prayer vigil in the Democratic Republic of Congo.
It is not clear how many died. The reported attack was the group's latest on villages in the north-east DR Congo.
Human Rights Watch says the LRA has killed at least 620 Congolese civilians and abducted more than 160 children since Christmas Eve.
Uganda, DR Congo and South Sudan last month launched an offensive on the LRA.
And the Central African Republic has sent troops to its border with DR Congo in an effort to push back the rebels.
Local residents said the LRA carried out the church attack on Saturday in a community just 130km (80 miles) from Dungu, which is the military base of Operation Lightning Thunder - the joint multi-national offensive on the rebels.
Felicien Balani, an official in Dungu, told Uganda's New Vision newspaper: "The LRA entered around midnight. They surprised the faithful of the church who were in a prayer vigil. They burned them in the church."
New York-based Human Rights Watch said it had unearthed evidence of a wave of killings by the LRA between 24 December and 13 January in DR Congo.
The organisation said in a statement: "At several sites where the killings took place, researchers found fresh graves, pools of dried blood, cords used to tie up prisoners and blood-stained bats and axes used to kill victims."
Last week the UN refugee agency UNHCR said the Congolese village of Duru was deserted after the rebels had attacked, looting, killing and burning.
The BBC has also received accounts of killings from the South Sudanese district of Mundri.
Two church parishioners who intervened after the rebels had abducted two boys had their hands and legs chopped off and were then beaten to death, said witnesses.
LRA leader Joseph Kony refused to sign a peace deal last year until International Criminal Court arrest warrants are withdrawn.
Over 100,000 people have fled suspected LRA rebels marauding across hundreds of kilometres stretching from the Central African Republic through Sudan and into DR Congo.
The LRA has been fighting in northern Uganda for two decades but is now based in DR Congo, most recently in the Garamba National Park.