Some of the heaviest fighting in months has broken out between Ethiopian forces and local insurgents in Somalia's capital, Mogadishu.
Insurgents turned to guerrilla warfare six months ago
Residents said that at least 10 people had been killed amid shell and machine-gun fire as the Ethiopian forces launched an offensive.
Somalia has seen a surge in violence since Ethiopian-backed government troops ousted Islamists last December.
Hundreds of civilians have been killed in the fighting.
The BBC's Africa editor Martin Plaut says the latest clashes began after Ethiopia moved reinforcements and a convoy of 20 tanks and armoured cars into the city late on Friday.
One of the vehicles was hit by a landmine and exploded.
Early on Saturday the Ethiopians fanned out of their barracks and fighting erupted.
The forces targeted areas of the city occupied by militia who are remnants of forces loyal to the ousted Union of Islamic Courts.
Insurgents are reported to have captured and ransacked a police station.
They later retreated chanting "God is great", witnesses said.
Local resident Ismail Osman told the Reuters news agency: "Ethiopian troops and insurgents are fighting in every alley."
The Ethiopian forces have since reportedly returned to barracks, but heavy artillery fire has continued.
A worker at one of Mogadishu's main hospitals said many people had been brought in suffering from gunshot and shrapnel wounds.
Local elders described the Ethiopian offensive as a genocide and have appealed to the international community to intervene.
Some 1,600 Ugandan troops are also in Mogadishu as part of a planned 8,000-strong African Union force to support the interim government.
Somalia has been without an effective government since the civil war began in 1991.
The UN says some 400,000 people have fled the violence in Mogadishu in the past four months.