"We assessed battlefields, spoke to civilians, visited hospitals and areas that were affected by the clashes," he said when asked how the figure was reached.
Somalia's Islamist movement has vowed to oppose foreign troops deployed to help the weak government consolidate its tenuous grip across the war-fatigued nation.
"We are not all prepared to allow invaders to trample upon our sacred rights and bring us under submission," Sheikh Sharif Sheikh Ahmed, head of the executive arm of the Union of Islamic Courts (UIC) said, following a meeting with Issaias Afeworki, Eritrea's president.
In a statement posted on Eritrea's information ministry's website on Monday, Ahmed said: "Somalis are united more than ever and their nationalism heightened."
'Worst in 15 years'
Without giving specifics Korgab said damage to property by the heavy fighting was an estimated "$1.5bn".
Humanitarian groups have described the clashes, most of which occurred in around the stadium area and Al Kamin neighbourhood in southern Mogadishu, as the worst in 15 years.
A local rights group, which compiled initial figures from hospitals and witnesses, said 381 civilians had died and 565 were wounded in the four days of clashes between March 29 and April 1.
Mike Hanna, Al Jazeera's correspondent in Bel Bur, 200 km south of the capital city, said that refugees heading out from Mogadishu to rural villages' to escape the violence could face a water and food shortages soon but it is possible for NGO's to resume operations. He also highlighted the lack of medical aid with Medical Sans Frontiers.
The UN refugee agency (UNHCR) said around 124,000 people, mostly civilians, have fled the blood-soaked capital in the past two months as a result of the violence.
Last week, Eric van der Linden, the European Union envoy to Nairobi, said he had asked Brussels to investigate whether Ethiopian-Somali forces committed war crimes in the bloody crackdown.
Somalia has lacked an effective central government since the ousting of former dictator Mohamed Siad Barre in 1991 touched off a bloody power struggle that exploded into inter-clan warfare.
More than 14 attempts to restore a functional government in Somalia have since failed.