Doctors in the self-declared republic of Somaliland say heavy fighting has killed at least 30 people.
Residents of Las Anod say they heard gunfire for more than six hours.
Somaliland broke away from Somalia in 1991 but has not been internationally recognised.
The authorities there have been in a border dispute with the regional government of Puntland. They both claim the Sool region, of which Las Anod is the capital.
The latest violence happened as traditional leaders announced that they no longer wished to be part of Somaliland and pledged allegiance to the Somali government in Mogadishu.