Speaking before the Senate Armed Services Committee, General Joe Votel said "somewhere between four and 12 casualties" resulted from the US raid, which was authorised by US President Donald Trump a few days after his inauguration.
"We have made a determination based on our best information available that we did cause casualties, somewhere between four and 12 casualties," which US forces "accept responsibility for," he said.
The January 29 raid -- the first authorised by Trump -- saw US special operations forces enter the Yakla region of Baida province and target a compound occupied by Al-Qaeda in the Arabic Peninsula (AQAP) operatives.
The mission was beset with problems and resulted in the death of a Navy SEAL as well as several non-combatants, including women and children.
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The US also lost a USD 75 million MV-22 Osprey aircraft.
The White House rejected criticism of the operation, saying it would be an insult to the SEAL who was killed, William "Ryan" Owens.
At least 22 alleged AQAP fighters have been killed in these raids since March 2.
Yemen's more than two years of civil war between government forces and Shiite rebels who control the capital have created a power vacuum, which AQAP has exploited to consolidate its presence in the south and east.