Violence between rival Ethiopian communities near the southern town of Moyale has escalated with eyewitnesses reporting that 13 people were killed on Monday.

Since the beginning of the month there have been sporadic clashes over land.

People from the Borana Oromo ethnic group complain that a referendum conducted in 2005 unfairly awarded what they consider to be their land to a Somali clan known as Garri.

Both are cattle herding communities and many herders carry guns.

Correspondents say ending the ethnic clashes in different parts of Ethiopia is the greatest challenge facing the reformist Prime Minister Abiy Ahmed.