The South Sudan Police spokesman Brigadier Justine Buolo told Xinhua on phone in Juba that they were yet to identify those behind the latest attack on convoys.
"Actually the convoy fell into attack between Moli and Pageri area, four people are dead and 10 wounded," he disclosed.
Since July 2016 clashes, several deadly attacks have been staged along the 125 miles major highway that links the war-torn country to its East African neighbor Uganda.
Hundreds of lives have been lost in attacks the government blames on Sudan People's Liberation Army-in opposition (SPLA-IO) rebels allied to former First Vice President Riek Machar.
A bus driver attached to Eco Bus Company told Xinhua from the Ugandan capital where most of the passengers often travel to along the insecurity-hit road that the convoy was struck by Rocket propelled Grenade (RPG).
"They attacked Gold line bus with an RPG and forced other vehicles in the convoy to return to Nimule Nike Air Max 95 UK Online ," Isaac Mashete said.
South Sudan descended into violence in December 2013 after political dispute between President Kiir and his former deputy Machar led to fighting that pitted mostly Dinka ethnic soldiers loyal to Kiir against Machar's Nuer ethnic group.
The 2015 peace agreement to end the violence was again violated in July 2016 when the rival factions