The slain civilians were travelling in a car in Bulla Marer, some 60km south west of the capital, Mogadishu when they were reportedly stopped at the blockade, resulting in soldiers opening fire.
The African Union Mission in Somalia (AMISOM), spokesman, Col Joe Kibet, confirmed the incident to CAJ News in Nairobi, Kenya.
The reportedly failure to follow troops’ orders prompted fears the four were members of Al Shabaab, a Somali affiliate of the Al Qaeda terror group.
The action by forces has sparked outrage among members of the community.
Abdiwahid Ibrahim Maalim, a son of one of the deceased, said his mother and granddaughter were in the car with two of his friends when the AU forces opened fire.
Local residents in Lower Shabelle have embarked on protests against the killing.
The AU has in recent has deployed some 25 000 troops and law enforcers in Somalia in their intensified attempt to weed out the Al Shabaab.
In February, the sect killed more than 100 Kenyan soldiers after attacking an AU base in El Adde close to the border with Kenya.
– CAJ News