Gunmen in southeastern Kenya have killed at least 11 people in an apparent revenge attack that is part of a long-running ethnic dispute over grazing land and water.

Kenya's Red Cross and government officials say fighters from the Orma community carried out the attack on the rival Pokomo clan early Friday in the remote Tana Delta region of Coast Province.

It appears to be retaliation for an August raid by Pokomo fighters on an Orma settlement in the same region that left more than 50 people dead. Tensions have remained high between the two communities despite government attempts to broker a peace deal.

The two communities have fought over resources for years, but officials believe there is also a political element at play. Kenya's defense minister has ordered an investigation of an assistant minister accused of fanning violence in the region.

The clashes between the pastoralist groups are also blamed on disputes sparked by land, grazing, or water resources.