Ron Redmond, spokesman for the U.N. High Commissioner for Refugees (UNHCR), told a news briefing in Geneva initial reports found "an irregular armed group" carried out an attack on the Awa tribe in the remote southwestern jungle region of Narino and killed 17 people.
Within Colombia, unconfirmed reports from villagers and other sources put the death toll from the attack at between eight and 17. They said FARC rebels killed the civilians because they accused them of backing the Colombian army in its crackdown on the leftist guerrilla group.
Because the area of the attack is inaccessible and insecure, the Colombian government faces challenges in ascertaining what happened.
The UNHCR said the killings could spur an exodus among the Awa.
"The rest of the population is now extremely frightened amid increasing concerns over a mass displacement of people in the days to come," Redmond said in Geneva, where the UNHCR has its headquarters.
The 21,000-person Awa community has been caught in the cross-fire of crime gangs battling Marxist guerrilla groups for cocaine-producing land in Narino, which lies on a major route for traffickers shipping drugs to the United States and Mexico.
"Apparently (the FARC) stabbed a number of Indians to death, accusing them of collaborating with the army," said local Governor Antonio Navarro, adding that poor security in the area was hampering plans to send in an investigative commission.
Navarro and indigenous leaders said rebels have planted landmines to halt the army's advance.
Redmond said the Awa people "have been subjected to severe rights violations, repeated murders and force displacement," with some seeking refuge in neighboring Ecuador as a result.
He said such violence had pushed more than a third of Colombia's 87 indigenous tribes to the brink of extinction.
