The deadly chaos prompted U.N. Secretary-General Ban Ki-moon Monday to express his concern about the situation in the African nation, the international organization said in a news release. Ban called on those responsible for the fighting to stop the "indiscriminate and disproportionate use of force" that was taking such a heavy toll on civilians in violation of international law.

Local sources told the U.N.-affiliated IRIN information agency hundreds of families had fled Mogadishu as weekend fighting claimed dozens of lives and left scores wounded.

"What we have seen on Saturday and Sunday was the worst fighting ever," said Asha Shaur, a civil society spokeswoman. "It was the most intense and destructive the city has experienced."

The IRIN reported that a journalist said the real toll may not be known for days, though fighting had subsided Monday. Government officials were unavailable for comment.

The Voice of America reported the dead included at least nine people found in a mosque, including several clerics with a Sufi Islamic sect. VOA reported that a resident, Ali Hersi, claimed Ethiopian troops carried out the carnage.

"People were collected from their homes and they were killed deliberately," Hersi said. "They were not fighting. Most of them were elders."

A spokesman for Ethiopia's Ministry of Information dismissed the allegations.