Rwandan rebels have killed 13 villagers in eastern Democratic Republic of Congo, a provincial governor has said.
The FDLR wants security guarantees before returning to Rwanda
The attacks in Kigalama were carried out at night by militiamen wielding machetes and guns, said the governor of South Kivu, Didace Kaningini.
He said the rebels from the Democratic Liberation Forces of Rwanda (FDLR) carried out the attack as they were fleeing from UN peacekeepers.
The FDLR, blamed for involvement in the 1994 Rwanda genocide, denied the claim.
The UN - which has 3,000 peacekeepers in the area - said it would investigate the incident.
The attack took place in Kigalama, about 130km (80 miles) south-west of the provincial capital, Bukavu, despite recent operations carried out by the UN to secure the area.
"Thirteen people were massacred... in Kigalama, " Mr Kaningini was quoted as saying by AFP news agency.
"The FDLR surrounded the village and began to fire. People fled and were killed, most of them by crude weapons, as they were trying to escape.
An FDLR spokesman denied the accusations.
The spokesman added that the only way to bring stability to central Africa would be to open political negotiations between the FDLR and the government in Rwanda.
Thousands of Rwandan militiamen entered eastern Congo after the 1994 genocide in which about 800,000 people - mostly ethnic Tutsis - were killed.
The rebels - ethnic Hutu - have repeatedly said they do not want to go back to Rwanda unless they are granted amnesty.
The UN began a joint operation with the Congolese army earlier this week to flush out the rebels after they failed to comply with an ultimatum to pull out of the area.
The rebels' presence has led to years of fighting in eastern Congo.
Rwanda has twice invaded, saying it is trying to wipe out the rebels. They were supposed to have been disarmed under a 2003 peace deal.