Other witnesses said that minibuses filled with armed men rushed to join the battle.

"I also saw insurgents evacuating some of their men ... but I am not sure whether they [evacuees] were dead or not," he said.

The civilians were killed by stray gunfire and shelling as troops responded to the attack, residents said.

Civilian anger

Hundreds of civilians celebrated in the Baruwa neighbourhood as the bodies of two dead soldiers were set on fire and dragged through the streets.
 
The crowd shouted: "You and Ethiopians will die", "Down, Down with Somali troops", and "We will burn you alive".

In another area, three bodies pulled around on the end of a rope, kicked and then also set alight, witnesses said.
 
Mortars were fired when the Somali and
Ethiopian soldierss came under attack [EPA]
Ethiopia sent soldiers into Somalia in December to help its ally in the interim government to defeat the Islamic Courts Union which controlled much of central and southern Somalia, including Mogadishu.

Soldiers from both armies have been struggling to restore security to the city since they regained control of it in late December and come under attack almost daily on the streets and in their bases.

Macharia Munene, professor of international relations at the United States International University in Nairobi, told Al Jazeera that it appeared fighters from the Islamic Courts were regrouping.

"They went into the civilians and took time to regroup and strategise, he said. "This appears to be what they were intending, to come together and launch a counter-attack ... to drive out not only the government but also the Ethiopians."

Somali leaders have said in the recent weeks that they were preparing a major offensive to stop the attacks as the government prepares to move its base to Mogadishu.

'Decisive' fighting

A group called the Popular Resistance Movement in the Land of the Two Migrations claimed they had been the target of the offensive that began early on Wednesday.

The group said in a statement posted on the website of the Islamic Courts Union that it had repulsed the attacks and an unspecified number of government soldiers had surrendered to them.

The group added that more fighting in the coming days would be "decisive".

A spokesman for the African Union forces, that have been deployed to help the Somali government regain control, said that they had not been  involved in the fighting.
  
"So far, we have not been counter-attacking at all. We are still in the phase of settling down the whole operation," Captain Paddy Ankunda, who is in charge of the 1,500 Ugandan troops already deployed, said.

Meanwhile, a United Nations spokesperson told Al Jazeera that a bomb exploded on a road on which a group of UN staff were travelling, injuring three Somali policemen.