At least 10 people have been killed in a second day of heavy fighting between rival militias in the key Somali port of Kismayo.
Witnesses say forces loyal to the leader of the Raskamboni group, Ahmed Madobe, battled gunmen led by a local leader, Ifti Hassan Basto. Both men claim to be president of Somalia's newly created Jubaland region.
Reports say Raskamboni forces now control a part of Kismayo.
More than five people were killed when the two forces battled for the first time on Friday.
The latest fighting has ignited fears as some residents have started fleeing. Businesses remain closed as people hide indoors.
Somali President Hassan Sheikh Mohamed called on Saturday for an immediate end to the fighting. The U.N. envoy to Somalia, Nicholas Kay, urged all parties to resolve differences peacefully.
"This new chapter in Somalia's history must be one in which issues are resolved peacefully. More violence will only prolong the suffering of Somalis and delay the revival they and the international community are working for," he said.
Kismayo is one of Somalia's busiest ports and an important source of revenue for whoever controls it. The militant group al-Shabab ran the city for several years before being pushed out by African Union forces and Raskamboni last year.
The Somali government formed last year has been trying to extend its authority to Kismayo and other parts of the country, but many militia groups continue to operate. Al-Shabab also remains active.
Some information for this report was provided by AFP and Reuters.