Fighting broke out before dawn on Saturday between Somali soldiers backed by African Union forcesand Al Qaeda-linked insurgents, leaving four civilians dead, while fresh clashes erupted in the evening, killing another 11, the sources said. The AU said at least six Shebab foreign fighters were also killed.
"We have collected the dead bodies of five civilians killed in the crossfire last night. Twenty-one others were also injured," said Ali Muse, who heads Mogadishu's ambulance services.
"I don't have details on this morning's casualties yet as sporadic fighting is still going on around the disputed areas," he told AFP.
Most of the fighting is centered around the southern districts of Hodan and Holwadag but shells also stray into neighbouring districts.
Witnesses said six more civilians, three of them siblings, died after a mortar shell struck their home.
"There has been heavy shelling and exchanges of gunfire in Holwadag district since last night. This morning three civilians died after a mortar shell hit their house in Bakara while two others were caught in the crossfire nearby," Hasan Mahbub, a local resident, said.
Abdi Osmail, another witness, said his brother was also killed this morning as he rushed to open his shop in Bakara market, a stronghold of the Islamist Shebab insurgents.
"People are dying for no reason, even far from where the fighting is going on. My younger brother... was hit by a stray bullet as he was going to open his shop," he said.
Abdikarin Yusuf Adan, Somalia's deputy army chief of staff, told reporters the military would continue to battle the insurgents until the Shebab threat is completely eliminated.
"We are achieving some landmarks in the fight against the violent elements and we will continue fighting until we rid the country of the Shebab," he said.
As is always the case when fighting breaks out in Mogadishu, the other side also claimed to have the upper hand.
"The invading Christian forces and their apostate allies attacked our positions yesterday and we struck back late yesterday, inflicting heavy losses on them," Sheikh Abdulasis Abu Musaab, a Shebab spokesman, told reporters.
"The reports we are getting from our mujahideen (holy warriors) commanders indicate that at least fifteen Christian soldiers were killed and many of their apostate allies. We have also seized arms caches containing machineguns."
The Shebab accuse the country's transitional government of being Western stooges and the African Union contingent of Ugandan and Burundian soldiers of being on a crusade against Muslim Somalia.
The AU mission (AMISOM) spokesman, Bahoku Barigye, claimed his troops killed several Shebab combatants in the clashes, including foreign fighters.
"We killed six foreign fighters and many of their Somali fighters that I cannot number but the fighting was very heavy," he told AFP.
Barigye said the foreign fighters AMISOM identified were from Pakistan, Yemen, Kenya, Syria and India.
The clashes came after a period of relative calm in Mogadishu, where Shebab insurgents have been attempting to break the weak Western-backed transitional federal government's last defences for close to two years.
Civilians have borne the brunt of the fighting for control of Mogadishu, with thousands killed and hundreds of thousands displaced over the past four years.