As many as 19 people have been killed and eight others injured after gunmen attacked a public bus in western Ethiopia, an official said. \"The attack took place Monday around 2 pm [in Gambella region]...I suspect it was an anti-peace element, we consider as rebels,\" AFP quoted regional president, Omot Odeng Olol, as saying on Tuesday. He said the assailants, armed with machineguns, robbed the passengers of their money and clothes before opening fire on the vehicle and its occupants. \"That kind of thing is the very worst you can imagine,\" the official said. The attackers fled the scene immediately. The police have launched an investigation to track them down. No one has claimed responsibility for the attack. Ethiopia\'s Gambella region, which lies some 700 kilometers (430 miles) to the west of the capital Addis Ababa, has witnessed several conflicts between rival communities in the recent past.