Ethiopia said on Saturday that gunmen from South Sudan had killed 140 people in a raid in its Gambela region, and that Ethiopian troops had crossed the border to pursue the attackers.
The attack took place on Friday in the Jakaya area that straddles the border, in a region that hosts alongside a neighboring province more than 284,000 South Sudanese refugees who fled conflict in the world's youngest nation. The region sits on the Ethiopian-South Sudanese border.
South Sudan gained independence from present-day North Sudan in July 2011. The separation resulted in ethnic tensions, and in December 2013 sectarian conflict emerged months after President Salva Kiir sacked his deputy Riek Machar as vice president.
This reopened a political dispute and ethnic rifts between Kiir's Dinka ethnic group and Machar's Nuer.
The gunmen had no relation to South Sudanese government troops or rebel forces who fought the government in Juba in a civil war that ended with a peace deal signed last year, the body said.
"140 civilians died in the attack carried out by bandits that crossed from South Sudan," a statement from the government communications office said, according to Reuters.
Machar said last week he would return to the capital Juba on April 18 to form a transitional government with Kiir.
Ethiopia's Gambela region has a sizeable Nuer population as well.
The South Sudanese government has come under fire recently for encouraging allied militias to rape and pillage in lieu of being paid.
“Fighters from pro-government militia which fight alongside the Sudan People's Liberation Army (SPLA) are compensated under an agreement of 'do what you can and take what you can ... ' Most of the youth therefore also raided cattle, stole personal property, raped and abducted women and girls as a form of payment," a United Nations report said.