"The victims could be more, but those who were brought to the hospital are 56," the source said on condition of anonymity.
Traffic has been heavy along roads linking South Sudan with its neighboring countries since last September, when violence erupted between government troops and fighters loyal to former South Sudanese vice-president Riek Machar.
The conflict in the newly-born country together with the deteriorating humanitarian conditions have forced hundreds of thousands of Southern Sudanese to flee to Ethiopia, Kenya, Sudan and Uganda.