The United States Africa Command issued a statement on Sunday, saying that "one (1) US service member and two (2) Department of Defense contractors were killed at a Kenya Defense Force Military Base in Manda Bay, Kenya".
According to the statement, two more DoD members who were wounded "are currently in stable condition and being evacuated".
"At this time, the names of the fallen and the wounded are being withheld as part of the next of kin notification process. Out of respect for the families of the fallen and injured, we ask that everyone respect their privacy during this difficult time. The Department of Defense is fully committed to providing the families of the fallen dedicated care, service, and support", according to the statement.
Earlier in the day, the Somali-based Islamist group, Al-Shabaab - affiliated to al-Qaeda - attacked a military base in Kenya's Lamu county.
The news comes after a deadly terrorist attack struck Kenya earlier this month, allegedly carried out by Al-Shabaab militants.
Washington said that the Pentagon carried out several air raids in the region targeting Al-Shabaab militants following the deadly attacks.
* Daesh (Islamic State, ISIL, ISIS, IS) Al-Shabaab, al-Qaeda are terrorist groups banned in Russia and many other countries.