Allied forces in Sanguni locality have vacated their military base on Sunday after two consecutive deadly attacks by Al-Shabab.
Al-Shabab fighters on Friday attacked the base from different directions leading clashes between the troops at the base and Al-Shabab fighters.
According to statements by both Al-Shabab and U.S. military, the fighting caused the death of one U.S military soldier and injuries of four others.
Somali Military officials who sought anonymity have confirmed the withdrawal of U.S. and Somali troops.
The officials said the U.S. forces were airlifted from the base just hours after Al-Shabab suicide car bomb hit the base leading injuries of seven soldiers.
Somali forces have reportedly moved from the barrack heading to Yontoy village which lies 20km outside Kismayo town.
Al-Shabab which claimed the responsibility of last night's suicide bomb has said the blast killed 40 soldiers.
"We killed 40 Somali soldiers in the base," Abdiasis Abu Musab, al Shabaab's military operations spokesman, told Reuters.
"The foreign forces ran away from the base this morning because we attacked them on Friday. We targeted the Somali forces that were in the base," he added.
Somali government and Jubbaland authorities have not yet commented on the recent incidents at the base.
Over 500 American troops are in Somalia, mostly composed of a number of Special Operations units, including Army Green Berets, Marine Raiders and Navy SEALs spread across the country.