Clashes between rival Somali clan militias in Kismayu killed 11 on Saturday, witnesses said, in the worst unrest since Kenya-backed pro-government forces recaptured the southern port from Islamist insurgents last year.
The fighting erupted when a clan leader died at a police station, prompting pitched battles between Marehan and Ogadeni clansmen, two of the three groups that have traditionally fought for control of Kismayu.
"I saw at least 11 people, especially fighters, killed in these battles," a Kismayu elder, Mohamed Ga'al, told AFP.
"It's the worst fighting since the Shabaab left the city, and even if the situation is calm now, the two sides continue to regroup," Ga'al added by telephone from capital Mogadishu.
Another witness, Ali Moalim Suleman, said three of the people killed were civilians caught in the exchange of fire, adding that six other civilians were wounded and taken to hospital.
In a statement Saturday, Somali Prime Minister Abdi Said Shirdon called on the two clans to lay down their arms.
"We are shocked to learn that two fraternal clans are fighting and spilling innocent blood, while residents await the establishment of a regional government."
Several clans have fought for control of Kismayu since September, when a Kenyan army contingent drove the Shabaab -- an Islamist insurgent group with ties to Al-Qaeda -- out of its main stronghold.
Witnesses said the Kenyan soldiers still stationed in Kismayu did not intervene to end the clashes.
Prior fighting between the militias had resulted in several deaths in December in Kismayu, which as Somalia's second largest port is vital to the country's economy.
The Kenyan troops, from the African Union Mission in Somalia (AMISOM), drove out the Shebab with backing from Somali forces, including the Ras Kamboni militia.
The militia, mainly made up of Ogaden clan members, is commanded by warlord Ahmed Madobe, who switched from supporting the Shabaab to fighting alongside the African Union.
Other clan militias have since been deployed in Kismayu, with clan rivalries posing one of the greatest threats to a return to peace in Somalia since AMISOM significantly weakened the Shabaab.
The port is of strategic importance as it lies at the mouth of the Jubba river and half way between the capital Mogadishu and the Kenyan border to the south.
The Ogadeni, Marehan and Majerteen clans that are dominant in the city and its surroundings have fought over the city since the 19th century.
Under the leadership of warlord Barre Hiraale, the Marehan in 2001 launched the Jubba Valley Alliance, in a bid to assert the clan's control over Kismayo.
Other political ventures such as the self-proclaimed statelets of Jubbaland and Azania have been attempted in recent years, with no credible leadership emerging to secure the region.