Fighting between militias in Somalia's central Galkayo city killed at least 29 people and wounded more than 50, officials from both sides said on Monday.
Colonel Mohamed Aden, a military officer from the semi-autonomous region of Puntland, said 16 soldiers serving in the region's army had been killed and 30 been wounded since fighting broke out again on Sunday.
The region of Galmudug had 13 soldiers killed and 20 wounded, said Hirsi Yusuf Barre, the mayor of southern Galkayo.
The two regions have a history of clashes and the latest round of fighting erupted after a dispute over buildings planned in Galkayo, a city that is divided between the two sides.
But before Sunday's clashes, there had been a week-long ceasefire in place.
Galmudug and Puntland are clashing in the town, which straddles their common border and is divided under the control of rival clan militias. As violence between these groups began to escalate a month ago, schools in Galkayo were forced to close and some people fled the town.
Under terms of a ceasefire deal mediated by Dubai and which was welcomed by the two sides and Somalia's federal president, forces of both regions were supposed to be withdrawn from the disputed area this past week.
The deal also called for those who had fled Galkayo because of previous fighting to be allowed to return.
Somalia has been gripped by conflict since the downfall of Mohamed Siad Barre in early 1990s, and the armed al-Shabab group has been one of the main causes of unrest in the past two decades.