The armies of the breakaway Somaliland and Puntland states early Thursday engaged each other in heavy fighting, reports said.
Both sides reportedly used light and heavy guns in the clash at Tukaraq District, about 1,100km northwest of the Somali capital Mogadishu.
The casualty figures were not immediately available.
Somaliland and Puntland have had long-standing border disputes, particularly over Sool and Sanaag regions that separate them.
Somaliland controls most of the disputed territories.
Troops from the breakaway Somaliland seized Tukaraq town from Puntland in January this year, and the two sides have since engaged in intermittent gun fights.
Failed to win
Somaliland in the northwest, declared independence from the rest of Somalia in 1991, but has since failed to win international recognition.
Puntland was established as a semiautonomous authority in 1998, but remains a member state of the Mogadishu-based federal government of Somalia.