Gunmen suspected to be from Ethiopia's Amhara region killed 26 people and injured 15 in an ambush on a vehicle carrying militia in neighbouring Oromiya, local officials said on Thursday.
Ethiopia has struggled to contain violence in its ethnically-based regions in recent years. The Oromo are Ethiopia's largest group and the Amhara its second, with frequent attacks on both sides of their border, mainly over land.
Tuesday's raid targeted a vehicle carrying about 100 militia members as it passed through the town of Korke in Oromiya, said Ababu Wako, head of the East Shewa district, about 170 km (105 miles) southeast of the capital Addis Ababa.
