The U.S. military said one U.S.
The attack by suspected Al-Shabaab militants occurred on Friday in Somalia's southern Jubaland province, where a small joint US-Somali outpost came under small arms and mortar fire, US defense officials said.
Four american military officials wounded during an Al-Shabaab attack in Somalia, are treated for their injuries and discharged.
The coalition force was conducting a "multi-day operation" to clear al-Shabaab, an Islamist militant group, from nearby villages.
President Donald Trump in early 2017 approved expanded military operations against al-Shabab, leading to an increase in USA military personnel to more than 500 and the launch of dozens of drone strikes.
The New York Times reports that al-Shabab has claimed responsibility for the attack.
US President Donald Trump offered his "thoughts and prayers" to those killed and wounded.
Associated Press video on Friday showed Somali forces firing weapons from atop pickup trucks in a muddy rural area, and an unidentified USA soldier speaking with local residents.
Since being pushed out of Mogadishu in 2011, the group has lost control of most of Somalia's cities and towns. Three of the wounded USA service members and the one local fighter who was wounded in the attack were medically evacuated, the Pentagon said. It was unclear whether all 800 US, Kenyan and Somali troops were present when the attack took place.
Late a year ago US drone strikes also began targeting a small presence of fighters linked to the Islamic State group in Somalia's north.
The U.S. team was backed up by armed surveillance aircraft, the officials said.
"The mission's objectives were to clear al-Shabaab from contested areas, liberate villages from al-Shabaab control, and establish a permanent combat outpost created to increase the span of Federal Government of Somalia (FGS) security and governance", said the Africom statement.
The extent to which USA troops are assisting behind the scenes or fighting shoulder-to-shoulder with local troops has become a point of contention, not only in Somalia but also in other parts of the world where US forces are helping fight extremist groups by backing proxy forces. Names of the soldiers were not immediately released, while next of kin were notified.