Ethiopian-backed Somali government forces have launched an offensive against insurgents after simultaneous attacks in the capital, Mogadishu.
The Ethiopians are not popular in Somalia
At least six Ethiopian bases in the city were targeted on Tuesday night by Islamists. Three civilians have died.
Correspondents say rocket-propelled grenades, hand grenades and machine guns were used in the attacks.
The attacks came after Ethiopia's prime minister said his forces are unable to withdraw from the conflict in Somalia.
Meles Zenawi said he had expected to withdraw his soldiers earlier in the year, once the Islamists had been driven out of Mogadishu.
But he said not enough peacekeepers had arrived and divisions within the Somali government had left it unable to replace the Ethiopians.
Their presence is unpopular in Mogadishu. Earlier this month, insurgents dragged the bodies of Ethiopian troops through the city.
The BBC's Mohammed Olad Hassan in Mogadishu says Ethiopian lorries and tanks can be seen patrolling the streets.
Those civilians that have not fled the city are remaining indoors, he says.
The attacks took place simultaneously at about 1930 local time on Tuesday night.
At least six Ethiopian army bases came under fire:
- In the north of the city at two former factories and at Ex-Control intersection
- In the south of the city at the football stadium and an army camp
- In the central Bakara market district where there are bases along the main road.
About three civilian bodies have been found on Wednesday morning around one of former factories.
Some 600,000 people have left Mogadishu this year
The dead civilians are said to have been on a bus that was caught in retaliatory fire from Ethiopian troops.
Mogadishu city council spokesman Mohamed Muhyadin has told the BBC there was another attack at midnight.
Militias in Somali army uniforms attacked a building housing government soldiers near Mogadishu International Airport.
One soldier was killed in the attack, he said. The number of Ethiopian casualities are not known.
Correspondents say troops have been sent to the area near the airport to hunt down the insurgents.
The UN refugee agency says 60% of Mogadishu residents have left their homes, including 200,000 this month, following the latest clashes between insurgents and the Ethiopian-backed government.
Our correspondent says the insurgents say they have been encouraged by the admission by Mr Meles that his forces were becoming bogged down in Somalia.
On an Islamist website, the insurgents said they were winning the struggle, and called for further attacks on the Ethiopian forces.
Only 1,600 Ugandan peacekeepers have arrived, from a planned 8,000-strong African Union force.
Somalia has not had a functioning national government since President Mohamed Siad Barre was overthrown in 1991.