The fighting took place in the base of the Jubbaland state on the outskirts of Kismayo in the Lower Jubba region.
The fighting erupted after Al-Shabaab militants reportedly attacked a Jubbaland military base in Bar-Sanguni area, and the fighting lasted for more than an hour.
Witnesses said they heard gunshots from both sides, and there were casualties, but said they could not confirm the exact number of casualties.
According to reports, one Jubbaland soldier was wounded in the fighting in Bar-Sanguni area.
Jubbaland security officials have not yet commented on the fighting, which comes as Jubbaland security forces recently arrested members of Al-Shabaab in an operation on the outskirts of Kismayo.