Quoting own sources, UN officials on Thursday said that half of the victims in last week's clashes were civilians.
They were caught in cross-fire and bombardment by artillery and other heavy weapons in parts of the south and in capital Mogadishu, the officials said.
Fresh violence erupted in Mogadishu on Wednesday night, the officials said.
Last week's factional fighting was the heaviest in months. There was no word on casualties on last night's fight in Mogadishu.
The fighting came at a time when warlords and clan leaders were trying to restore a central government at reconciliation talks hosted by neighbouring Kenya.
But the 18-month-old process has been dogged by rifts between Ethiopia and Arab states, rivals for influence in the Horn of Africa.
"We are shocked…and deeply concerned over the plight of the many civilian inhabitants of the city who have been struggling for many years to achieve a measure of peace," said Winston Tubman, the UN secretary-general's representative for Somalia.
On Monday, Medicines sans Frontiers temporarily withdrew its international staff from the southern Somali town of Dinsor where it runs a small hospital after finding a new landmine on the runway of a local airstrip.
The south is the most volatile pocket of the country of more than seven million which collapsed into lawlessness after the overthrow of military ruler Muhammad Siad Barre in 1991.
Conflict and famine have killed hundreds of thousands of people since then.