At least 17 people have been killed and dozens more wounded in fierce fighting between government forces and members of a Muslim group in the Somali capital of Mogadishu.
An emergency official said 11 people were killed and 22 others wounded in one attack on Thursday, when an artillery shell struck a building where families had sought shelter.
Five children and three women were killed in the blast, Ali Muse, the head of
Mogadishu's ambulance service, said.
"It was a grisly scene. I haven't seen such a massacre in recent days,'' he said.
The fighting between Somali troops and anti-government fighters killed six civilians earlier in the day, Muse said.
Twenty-one civilians were wounded in the earlier fighting.
The Red Cross on Thursday expressed shock at the repeated shelling of a hospital in Mogadishu that killed at least one patient in the past three days.
"We are shocked about the situation at Keysaney [hospital]," Pascal Mauchle, head of the International Committee of the Red Cross (ICRC) delegation in Somalia, said in a statement.
"The situation is becoming more and more dangerous for patients and medical staff by the day."
A first shell on Tuesday left one patient dead and another wounded.
According to the ICRC two more mortar shells hit the hospital on Thursday, damaging the building.
Somalia's fragile, UN-backed government, established in 2004, has been battling Islamist fighters who control much of the country's south and centre.
The government controls only a few blocks of Mogadishu and relies on African Union peacekeeping troops to protects key government officials and installations.
Somalia has not had a functioning government in nearly 20 years.
Ban Ki-moon, the UN secretary-general, urged Somalis to seek unity in their divided country, which marked its 50th independence anniversary on Thursday.
Somalia gained independence from Italy in 1960 and merged with Somaliland, a British protectorate that proclaimed independence five days earlier.
Somalia has been mired in civil war since 1991.