Sheikh Abdirahin Ise, an anti-government fighter, told AFP news agency: "The fighting was so heavy and our holy warriors with the help of Allah won a huge victory."
"In return they [Ethiopian troops] killed pastoralists who were near the fighting zone."
The fighters have promised to avenge the killing of Aden Hashi Ayro - the leader of al-Shabaab, the former armed wing of the ICU.
Ayro, killed in a US air raid last week, was accused by Washington of being al-Qaeda's leader in Somalia.
Ethiopian troops entered Somalia in 2006 to rescue an embattled transitional government.
The ICU has since been fighting government forces, its Ethiopian allies and African Union troops.
Separately, on Wednesday, a truck driver contracted by the World Food Programme (WFP), was shot dead in central Somalia by a gunman who opened fire at a convoy of trucks ferrying food.
Peter Goossens, the WFP's director for Somalia, said in a statement: "We condemn this senseless killing and once again urge all parties to ensure the safe passage of humanitarian staff and cargo across the country."
Violence has disrupted the delivery of aid to hundreds of thousands of internally displaced civilians in the country.
Humanitarian groups are struggling to feed at least two million people in Somalia, which is experiencing a prolonged drought and record high inflation.