Survivors say at least 109 people were killed late last month by the Tutsi-led army in Ruyigi and Rutana, two provinces along Burundi's eastern frontier with neighboring Tanzania, after Hutu rebel attacks in the area.
The army denied the charges.
''Burundian soldiers killed my family,'' an elderly man told Reuters in Bugama, about 75 miles east of the capital Bujumbura.
He said 37 civilians, most of them women and children, had been killed in Bugama on January 28 and 29 and local residents buried them in three mass graves there.
''They (government troops) were commanded by the local administrator of (neighboring) Bweru commune. Twelve members of my family were killed,'' he said, adding the dead including his wife and one son.
In a separate incident further south on January 25, villagers accused the army of killing 72 Hutu civilians in Rutana province at Rusunu and Rubano hills.
''I can confirm that we buried 52 dead bodies at Rubano and 20 at Rusunu,'' said a local resident, adding that most of those killed were schoolchildren between 12 and 14 years old.
Burundi army spokesman Colonel Longin Minani denied the killings took place.
''These accusations are false,'' he told Reuters. ''Whoever gave this false testimony belongs to the rebels.''
An estimated 200,000 people, mostly civilians, have been killed in Hutu rebel attacks and reprisals by the country's mostly Tutsi army since 1993.
Peace talks aimed at ending the conflict are set to begin on Monday in the northern Tanzanian town of Arusha under the mediation of former South African president Nelson Mandela.
Burundi's eastern provinces of Ruyigi and Rutana have been particularly hard hit by fighting between rebels and the army over the last few months.
A local human rights group, Ligue Iteka, says at least 585 houses, eight schools and two health centers were burned or destroyed in Ruyigi province between December and January alone.
Residents in the area also accused rebels of looting houses and fields in search of food and supplies.
''Rebels come here and loot our crops, take our money by force and beat us up, but they never kill anybody,'' said one Rusunu resident.
''The army accused us of supporting the rebels. How can we support them while they are looting our things?'' he said.
On Saturday, rebels looted and partly burned a health center several miles outside Ruyigi town, aid workers said.
- Reuters - Thomson Reuters Foundation
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