An American commando was killed in an attack in southern Somalia on Friday that also wounded four US military personnel and a Somali soldier.
The attack occurred in the Jubaland region, where a large force comprising about 800 Somali, Kenyan and US troops were clearing a large area of Al Qaeda-affiliated Al Shabab fighters.
The multinational force "came under mortar and small-arms fire at approximately 2:45pm Mogadishu time, killing one US service member and injuring four US service members and one partner force member," the US military's Africa Command said.
An Al Shabab spokesman told Reuters it had carried out the attack in the coastal town of Kismayo, and claimed a higher death toll.
"We attacked a military base ... killed one US soldier, two Kenyan soldiers and nine Somali soldiers from Jubbaland state. We also injured four US soldiers," Abdiasis Abu Musab said.
A military official said the dead American was a special operations commando, but further details were not being released pending notification of next of kin.
US President Donald Trump offered his condolences on Twitter.
"My thoughts and prayers are with the families of our serviceman who was killed and his fellow servicemen who were wounded in Somolia. They are truly all HEROES," Mr Trump tweeted, misspelling the name of the country.
The mission's objectives were to "clear Shabab from contested areas, liberate villages from Shabab control and establish a permanent combat outpost designed to increase the span of federal government of Somalia security and governance", Africa Command said.
"The US provided advice, assistance and aerial surveillance during the mission."
More than 500 American forces are working with the African Union Mission to Somalia (Amisom) and Somali national security forces in counterterrorism operations, and have conducted frequent raids and drone strikes on Al Shabab training camps throughout Somalia.
The US commando's death on Friday was the US military's first fatality in Africa since four soldiers were killed in ambush in Niger last October.
A Navy SEAL was killed in Somalia in May last year, marking the first US military combat death there since the infamous "Black Hawk Down" events of 1993, when 18 American servicemen died in the Battle of Mogadishu.
Al Shabab has been fighting to overthrow the internationally backed government in Somalia since 2007. The group was pushed out of the capital, Mogadishu, in 2011 but still controls some regions of the country.