Human Rights Watch says the massacre that took place last December in the Democratic Republic of Congo was previously unreported.
A human rights group says rebels in the Democratic Republic of Congo killed at least 321 villagers in a previously unreported massacre last December.
In a report issued Sunday, Human Rights Watch says Lord's Resistance Army rebels attacked at least 10 villages during a four-day rampage in Congo's northeastern area of Makombo.
The group says most of the massacred villagers were men who were tied up and killed by blows to the head or machetes. It says the dead included 13 women and 23 children, including a 3-year-old girl who was burned to death.
Human Rights Watch says the LRA also abducted at least 250 people from the villages, including 80 children.
It says the attack shows the LRA remains a dangerous threat, despite claims to the contrary from the DRC and Ugandan governments.
Ugandan forces have been chasing the LRA across central Africa since late 2008. The group was originally based in northern Uganda before evolving into a regional threat, active in the DRC, the Central African Republic and southern Sudan.
The rebels are accused of killing, kidnapping and mutilating thousands of people over the past 22 years. LRA leader Joseph Kony is wanted by the International Criminal Court on war crimes charges.
U.N. officials have confirmed the massacre and say the world body is investigating. U.N. investigation chief Liliane Egounlety told the Reuters news agency that her team has confirmed 290 deaths so far.
Officials say it has taken a long time to carry out the investigation because of the remoteness of the area.
The U.N. mission to Congo has about 1,000 peacekeeping troops in the general region. Human Rights Watch that number is far too low given the vast size of the area.