Fighting has erupted in the Somali capital, Mogadishu, reportedly between sections of the security forces supporting President Mohamed Abdullahi Mohamed and units opposed to him.
Witnesses reported hearing heavy gunfire in the streets.
Last week Mr Mohamed - known as Farmajo - controversially approved a two-year extension of his term in office. His mandate officially ended in February.
The move was strongly criticised by the UN and the African Union.
Details on Sunday's violence were sketchy. The privately owned Morad news website tweeted that heavy gunfire had broken out in north Mogadishu. It said the fighting was between pro-government forces and military units that support the opposition.
Caasimada Online, another privately owned website, said anti-government protesters were burning tyres parts of north Mogadishu were under the control of rebel soldiers.