Fifteen people have been killed in heavy fighting in Somalia's capital, Mogadishu, where angry crowds dragged soldiers' bodies through the streets.
Attacks against government forces are increasing
Crowds kicked the dead bodies and set them alight.
Hundreds of civilians have been fleeing the violence, which is the worst since Islamists were driven from power in December after six months of rule.
Some 1,200 African Union troops have been deployed to Mogadishu this month to try and bring stability to the city.
Dozens have been killed during insurgent attacks in Mogadishu in the past two-and-a-half months, which the government blames on remnants of the Union of Islamic Courts (UIC).
Ethiopian troops, who have been in the city since December supporting Somali forces loyal to the transitional government, have been gradually handing over responsibilities to the AU force.
The latest fighting started when pro-government forces tried to take control of strongholds of the Hawiye clan, whose leaders oppose the presence of Ethiopian forces.
The BBC's Mohammed Olad Hassan says Somali and Ethiopian troops, supported by tanks and armoured vehicles, entered an insurgent area of central Mogadishu before dawn.
They were met by hundreds of masked insurgents, the first face-to-face confrontation between the two sides since December.
Shooting and mortar fire started and quickly spread to other parts of the city and at least seven government soldiers were killed, our reporter says.
In the north-east of the city - an Islamist stronghold - photographs show people gathered around the body of a soldier killed during the fighting.
Other pictures posted on the Shabelle Media Network's website show the bodies of two soldiers being dragged through the streets.
Shabelle reports that one was a Somalia government soldier, the other an Ethiopian fighter.
Correspondents say the scenes evoke memories of events in 1993 when the bodies of US soldiers were dragged through the streets of Mogadishu by militiamen.
"This was a horrendous act and we are unhappy about the violence but this was something we expected because extremists elements are re-grouping in Mogadishu to sabotage the interim government," US envoy in Nairobi Michael Ranneberger told reporters.
Somalia enjoyed a six-month lull in the insecurity that had dogged the country for the past 16 years when the UIC took power last year.
But insecurity has returned to the city and the UN estimates some 40,000 people have fled from Mogadishu since February.
Our correspondent says there has been a dramatic escalation in attacks against government targets in recent weeks.
It comes at a time when the government says it plans to hold a national reconciliation conference in Mogadishu in April.
Insurgents may want to signal that the city is not safe to hold the meeting in, he says.
The US government has requested Congress to approve $60m to fund deployment of AU troops and support the national reconciliation conference planned for April, Mr Ranneberger said.