At least 12 people were killed in fighting on Friday between armed group and African Union peacekeepers in Somalia's capital and the government again called for more foreign troops against fighters.
The main armed group al Shabaab opposes Western-backed government and also presence of foreign troops.
Fighters from the al Shabaab group said they attacked government bases and AMISOM peacekeeping troops overnight and were then hit by shellfire themselves.
"This fighting was the worst in months," Mogadishu resident Ahmed Hashi told Reuters.
Violence in Somalia has killed 19,000 civilians since the start of 2007 and uprooted a further 1.5 million people, a contributing cause of one of the world's worst humanitarian emergencies.
At an AU summit in the Ethiopian capital Addis Ababa, Somali Foreign Minister Ali Jama' Jangeli called for more African Union troops to help soldiers from Uganda and Burundi in the capital.
His Kenyan and Sudanese counterparts backed the call. Djibouti said this week it would send 450 soldiers soon.
"The situation in Somalia is very grim, it is very precarious. It is threatening stability in the whole of the east Africa region and the Horn of Africa," Sudanese Foreign Minister Deng Alor told Reuters in Addis Ababa.
"It is in our interest as a region ... also in the interest of Africa to contribute more troops to Somalia so that there is law and order in Somalia," he said.
In a statement, al Shabaab claimed responsibility for the overnight assault and accused the AU of bombing civilians.
"The mujahideen attacked AMISOM and government bases last night and we killed some of their troops," the fighters said. "When we pulled back, AMISOM began intentionally shelling residential areas. We shall keep on targeting them."
An AU military source and a Somali government official, who both declined to be identified, told Reuters one Ugandan soldier was killed in the fighting and one wounded. Two peacekeepers were killed on Monday in a rebel mortar attack on an AU clinic.
At least 25 people were wounded in the latest clashes, an officer with the ambulance service told Reuters, mostly in the city's Hodan Wardhigley and Howl Wadag districts.
"We were woken up by the explosions at 2 a.m. and haven't slept since because of the non-stop shelling," said Nurta Hussein, another resident. "Two mortar bombs landed in this neighbourhood, killing four civilians and wounding six."
Reached by telephone on Friday, Somalia's state minister for defence, Sheikh Yusuf Mohammad Siad, a former warlord also known as "Inda'ade" or "white eyes", said government forces had killed more than 10 fighters during the overnight fighting.