Militias fought overnight in remote village 15km north of Mogadishu, witnesses said on Friday.
"At least 16 have died from both sides and several others wounded" Ibrahim Moallim, a member of a so-called anti-terrorism commanders' coalition, told Reuters.
"I saw one of our dead militiamen."
Aljazeera's correspondent in Mogadishu, Ehab al-Alfi, reported that the situation in the centre of Mogadishu was relatively calm on Friday, after the fighting shifted to Arfid, on the northern outskirts of Mogadishu.
This was a result of each faction trying to penetrate the front line of the other, he said.
In one incident on Friday, a man strapped a bomb to a motorcycle and left it in front of a shop in Bindiri district of northern Mogadishu, witnesses said.
The ensuring explosion killed four people and injured another four, while the man responsible for the blast escaped.
Aljazeera said the two deaths took the overall toll to 20.
Sources told Reuters that fighting had subsided by noon on Friday but the acrimony from the clashes sparked fears of more violence.
Some 350 people have been killed in three bouts of heavy fighting since the start of the year between fighters allied to Islamic courts and a self-styled anti-terrorism coalition of commanders that many believe is backed by the US.
Moallim Hashi Mohamed, who is allied with the Islamic court militias and whose fighters clashed with rivals backed by commander Muse Sudi Yalahow, vowed to retaliate and reclaim properties and the areas he had lost.
The lawless country is seen by
the US as a haven for terrorists
"Muse Sudi's militia attacked my station without any reason," Hashi told Reuters in Mogadishu. "We will take revenge as soon as possible."
Meanwhile, thousands of angry Somali Muslims denounced on Friday the US and a US-backed alliance vowing to destroy their opponents.
Chanting anti-US slogans and comparing George W Bush, the US president, to a "Nazi", some 5,000 Muslims gathered in southern Mogadishu and pledged to fight to the death against the alliance as fierce fighting raged north of the city.
Surrounded by heavily armed Islamist militiamen, the throng cheered as clerics accused Washington of financing a "genocide" in Somalia by bankrolling the Alliance for the Restoration of Peace and Counter-Terrorism (ARPCT).
"The United States is wrongfully supporting the warlords by funding them in this war," said Sheikh Sharif Sheikh Hamad, chairman of the coalition of Mogadishu's 11 Islamic courts.
"The US actions are contrary to international law and against the will of the Somali people," he told the crowd, which assembled after Friday prayers.
"We will fight and die for Somalia and Islam," said Sheikh Mohamoud Sheikh Ibrahim, a senior cleric in the coalition of Sharia courts accused by the US and the alliance of harbouring terrorists.
"The US actions are contrary to international law and against the will of the Somali people"
Sheikh Sharif Sheikh Hamad,
Coalition of 11 Islamic Courts
"We will die for the sake of Allah and we will emerge victorious in our war against the US proxies here," he said. "We will never be ruled by US-paid mercenaries."
Although also fuelled by commercial and political motives, such fights in and around Mogadishu are seen by many Somalis as a proxy war between Islamists and the US.
The US government has long viewed Somalia, without a central government since the 1991 ouster of former ruler Mohamed Siad Barre as a haven for terrorists.