Unknown gunmen on Thursday ambushed a convoy on the main road connecting South Sudan's capital with the Ugandan border, killing at least 15 people, officials said.
Nine others were wounded in the attack on a civilian convoy escorted by the military on the insecure Juba-Nimule highway.
"The convoy was attacked in Moli village when it was coming from Nimule to Juba with an escort," said South Sudan police spokesman Daniel Justine, who confirmed the death toll.
He said the convoy was "targeted with heavy weapons" and that gunfire struck a military vehicle and two private civilian vehicles.
Some of the wounded and the dead were taken to Juba's main hospital while others were transported to the border town of Nimule.
South Sudan's deputy interior minister Riaw Gatlier called the incident "unfortunate" and said an investigation was underway.
Thursday's ambush was the second this week alone on the Juba-Nimule road, after an attack on Monday left one dead and four injured.
The dangerous highway is nevertheless a lifeline for South Sudan, which imports almost everything, and for people fleeing the more than three-year-long civil war for the safety of refugee camps in Uganda.
Since the government began deploying military escorts for convoys using the road in January there have been at least four separate deadly attacks with no one claiming responsibility or held to account.