'We attacked a military base ... killed one USA soldier, two Kenyan soldiers and nine Somali soldiers from Jubbaland state.
"During an operation June 8, 2018, in Jubaland, Somalia, one U.S. Special Operations member was killed and four U.S. service members and one partner force was wounded as the result of an enemy attack", U.S. Africa Command (Africom) said in a statement.
One "partner force member" also was wounded.
A United States special forces soldier has been killed in an attack by suspected al-Shabab militants in south-western Somalia, officials say.
Four others were wounded as well during an ambush attack conducted by the Islamic extremist group al-Shabab in the southwestern part of the country.
The mission's objectives were to "clear Shabaab from contested areas, liberate villages from Shabaab control and establish a permanent combat outpost created to increase the span of federal government of Somalia security and governance", Africa Command said.
Hundreds of American troops now serve in Somalia.
The official did not immediately know who had carried out the attack, but the U.S. is supporting Somali partners as they target Islamic al-Qaeda militants aligned with the Shabaab group.
U.S. President Donald Trump expressed his condolences to the family of the deceased soldier in a tweet.
Al-Shabab, which is fighting to impose Shariah law across Somalia, was pushed out of the capital, Mogadishu, and other major urban cities more than two years ago. Names of the soldiers were not immediately released, while next of kin were notified. Al-Shabaab is an al-Qaeda affiliate operating to overthrow the Somalian government, and it took credit for the attack.
The October attack in Niger raised questions in Washington about the us military presence across Africa as the Trump administration focuses counterterror efforts on a range of groups linked to al-Qaida and the Islamic State group.
Late previous year USA drone strikes also began targeting a small presence of fighters linked to the Islamic State group in Somalia's north. A Pentagon investigation of the incident produced a highly critical report.