Clashes between militias in the Somali capital, Mogadishu, have left 13 people dead, days after some of the heaviest fighting seen in the city for years.
Both sides have been using lulls in the fighting to rearm
The latest violence has been centred in the Daynile and Galgalato districts.
Gun battles on Thursday killed at least 60 people, left scores injured and forced hundreds out of their homes.
Some 200 people have died in clashes this year between militias loyal to Mogadishu's Islamic courts and an alliance of warlords.
The fighting is the worst the city has seen for more than a decade.
Somalia has had no fully functioning government since the overthrow of President Siad Barre in 1991.
Saturday's violence comes after a brief lull on Friday.
"The two sides are regrouping and concentrating on attack rather than on defence," a retired military officer told the AFP news agency.
"According to my experience, these people are planning to continue with the violence for the days to come," he said.
Roadblocks had been set up by the rival militias in the Daynile district and both sides were reportedly using machine guns and mortars against each other.
Most of the casualties in the recent fighting have been civilians caught in the crossfire, according to witnesses.
The UN Secretary General, Kofi Annan, has called on all the sides to work towards a ceasefire and respect human rights.
Recent efforts by Somali clan elders to mediate between the rivals have failed to establish a lasting truce.
Thousands of civilians have been fleeing their homes to avoid being struck by rockets, shells and bullets.
The fighting has been fuelled by a widespread belief that the alliance of warlords is being backed by the US, according to our correspondent.
The US merely says it will support those trying to stop "terrorists" setting up but stresses its commitment to the country's transitional government, which functions from Baidoa, 250km (155 miles) north-west of the capital.
The Prime Minister, Ali Mohamed Gedi, has meanwhile ordered four cabinet ministers who are also warlords in Mogadishu to return to Baidoa.
According to the Associated Press news agency, Mr Gedi has written a letter warning the four ministers they face legal action if they fail to follow his orders.
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