MOGADISHU, Somalia - Islamic fighters ambushed an Ethiopian military convoy on Sunday, killing six soldiers and injuring 20 in the first known skirmish between the rival forces maneuvering for control in Somalia, witnesses said.

Displaced Somalian refugees past floodwaters at the Dadaab refugee camp in Kenya's northeastern province November 17, 2006. This week the UN said more than 78,000 people had lost their homes to floods in northeastern Kenya's Dadaab area, and three vast refugee camps there were completely cut off. Picture taken on November 17, 2006. [AP]

Two Ethiopian trucks were destroyed by land mines before Islamic fighters opened fire on the convoy of more than 80 vehicles, witnesses told The Associated Press. The convoy was headed for the town of Baidoa, 150 miles west of the capital Mogadishu, where the country's weak interim government is based.

Ethiopia backs the transitional government, whose authority has been severely challenged by an Islamic movement that has taken over the capital and much of southern Somalia since June.

The attack occurred near the town of Bardaleh, 50 miles southwest of Baidoa. Six Ethiopian soldiers were killed and 20 were injured according to a Somali fighter traveling in the convoy who asked not to be identified for fear of retribution.

"There were two explosions and then a large exchange of gunfire," said one witness who spoke on condition of anonymity for fear of reprisals. Around 50 Islamic fighters were involved, the witness added.

Islamic courts spokesman Sheik Abdirahim Ali Mudey told the AP that four Ethiopian trucks were destroyed and some soldiers were killed, but denied that his group was responsible for the attack. He said it was "a popular uprising" by village residents opposed to Ethiopian troops inside Somalia.

Heightening tensions in Somalia have raised fears of an all-out war could engulf the wider region.

Experts have warned the country has become a proxy battleground for Somalia's neighbors, Eritrea and Ethiopia. A confidential UN report obtained last month by the AP said 6,000 to 8,000 Ethiopian troops are in or near Somalia's border with Ethiopia, backing the interim government. The report also said 2,000 troops from Eritrea are inside Somalia supporting the Islamic movement.

Somalia has not had an effective government since 1991, when warlords overthrew dictator Mohamed Siad Barre and then turned on one another. The interim government was formed with the help of the United Nations two years ago, but it only controls Baidoa, the town where it is based.

Government officials confirmed a skirmish had taken place but said they had no details. They spoke on condition of anonymity because they were not authorized to speak to the media .

Ethiopian officials were not immediately available for comment. Ethiopian officials acknowledge sending military advisers to help Somalia's government, but have denied deploying a large number of troops.

Somalia's Islamic movement, meanwhile, lifted a curfew Sunday imposed after demonstrations against a ban on the popular stimulant "qat," a leaf chewed across the Horn of Africa and the Middle East. The 9 p.m. to 4 a.m. curfew imposed Thursday was the first in Mogadishu since the collapse of the last effective national government 15 years ago.