Somali Islamists say they will attack Kenya if it goes ahead with plans to train 10,000 government troops.
"We will order all our holy warriors to start the jihadi war inside Kenya," said spokesman Sheikh Muktar Robow.
Foreign Affairs Minister Moses Wetangula has been quoted recently offering the training to beleaguered government forces.
The warning comes as insurgents have again battled government troops and peacekeepers in the capital, Mogadishu.
At least five people have been killed, residents and doctors say.
A witness told the BBC there were clashes near an African Union peacekeeping base at the strategic K-4 junction and that mortars were used.
The Islamists have increasingly targeted the AU peacekeeping force in recent months, as well as the government and their Ethiopian allies.
The K-4 junction is strategically placed in the south of the city linking the airport and the presidential palace, and some AU peacekeepers are based there.
The witness said he could see houses on fire, and heavy gunfire could be heard in the background.
The government is recognised by the international community but correspondents say it only controls a few patches of the country.
Somalia has been without a functioning government since President Mohamed Siad Barre was ousted in 1991.
Ethiopian troops helped the government push Islamist forces from control of central and southern Somalia in late 2006, triggering an insurgency.
The US supports Ethiopia's intervention in Somalia and accuses the Islamists of links to al-Qaeda.
The US says they are sheltering al-Qaeda operatives who attacked Israeli targets in Kenya in 2002.
On Thursday, Ethiopian Prime Minister Meles Zenawi said Ethiopia would review its position in the coming months, but would stay longer if Somali politicians showed "readiness for peace".
Even if Ethiopian troops left, he said, they could still return if the powerful Islamist militia al-Shabab threatened to take power.
"Whenever there's a threat posed, we will come back to break their backs," he said.
"Any government is preferable to the Shabab. It's in the interest of Ethiopia and the Somali people to prevent them from coming to power."
More than three million people - almost half of Somalia's population - need food aid, according to the UN.
Aid agencies recently estimated that 1.1 million people had been uprooted from Mogadishu over the last nine months.
Last weekend, Burundi deployed more than 800 peacekeepers to Somalia, boosting the strength of the AU force to just over 3,000.
But the mission, which is made up of troops from Uganda and Burundi, remains well below the force of 8,000 that the AU originally said it would send.
Mr Meles said Ethiopian troops would remain in Somalia "at least until the African peace force is fully deployed."
6 months ago