Insurgents have launched simultaneous attacks on five government and Ethiopian military installations in the Somali capital, Mogadishu.
Hawiye and Islamist fighters want Ethiopia to withdraw
They are the most serious attacks since Ethiopian-backed forces battled Islamists and Hawiye clan fighters in April - the worst fighting in 16 years.
The attacks come a day after proposed peace talks were delayed for a month.
Ethiopian troops have been in Somalia since December, when they helped oust an Islamist group that had taken power.
Islamists and Mogadishu's dominant Hawiye clan are opposed to the presence of Ethiopian troops in the country.
The BBC's Mohammed Olad Hassan in Mogadishu says that the heavily armed attackers fired mortars and rocket-propelled grenades at three Ethiopian bases, the main football stadium and the defence ministry.
Mogadishu resident Nuuradin Jama told the BBC that the fighting he witnessed was very intense.
"Armed men attacked the Ethiopians and the Ethiopians opened fire indiscriminately into the civilian areas," said Mr Jama.
"We do not know who they were but we thought they were the insurgent groups because they wore turbans and dressed the style of the insurgents."
Meanwhile, gunmen killed a local government official early on Thursday.
Two men shot the district commissioner of the northern Shibis suburb, Abukar Hussein Hassan, as he walked to work.
The latest violence has sparked fears that violence may return to Mogadishu.
Last week, Ethiopia's prime minister pledged to withdraw his troops from Somalia once peace took hold in the capital.
Somalia has been without a functioning government since 1991.