State police in Myanmar say the military has sentenced six soldiers to 10 years in prison with hard labor for killing three civilians in war-torn Kachin state.

The Kachin state police office says a military tribunal handed down the sentence Friday after finding the soldiers guilty of killing three ethnic Kachin civilians in September. Kachin is home to an ethnic rebel army that has been fighting the Myanmar military for more than seven years.

The civilians were on their way back to their refugee camp when they were detained by soldiers. Their bodies were later found in a shallow grave.

Rights groups said the prosecution of the six soldiers was rare and is the first step down a long road to ending military impunity.