Soldiers loyal to Somalia's transitional government - backed by Ethiopian troops - are reported to have entered the capital, Mogadishu, after Islamist fighters left the city.
Fighters from the Union of Islamic Courts have been driven out of many Somalian towns, with many taken prisoner.
There has been no confirmation of the numbers killed, but the transitional government says its forces have killed between 2,000 and 3,000 Islamists.
Ethiopia, which backs the transitional government, began a major offensive last weekend, hoping to topple the Islamists.
The fighting in Somalia began earlier this month. Thousands of civilians and soldiers are believed to have been injured.
Troops belonging to the transitional government now control most of the country.
The Islamists have been forced back to their last stronghold at Kismayo, in Somalia's south, but insist they have not been defeated.
Many civilians have been fleeing the fighting, taking whatever they can with them.