Oil-rich South Sudan plunged into civil war in December 2013 and a third of the population has since been displaced.
The travel advisory comes a day after two Kenyan pilots who had been abducted by South Sudan rebels returned home.
Kenya has issued a travel advisory to its citizens living in South Sudan.
The Ministry of Foreign Affairs urged Kenyans to move away from and avoid travelling to areas where armed conflicts and inter-ethnic violence have occurred within the last six months.
The advisory, the ministry said, applied to parts of the Greater Upper Nile region, particularly the states of Bieh, Latjoor, Akobo, Jonglei, Northern Liech and parts of Maiwut, Eastern Nile, Boma and Yei River.
Oil-rich South Sudan plunged into civil war in December 2013 and a third of the population has since been displaced.
Efforts to broker peace have failed as agreements are violated soon after they are signed by both government forces and rebels.
Kenya on Wednesday advised its citizens living in other parts of the war-torn country to exercise extreme caution.
“Avoid unnecessary travels in these regions because the security situation is risky,” the statement from the ministry read adding that Kenyans "security cannot be guaranteed.”
All Kenyans in South Sudan who are yet to registered were asked to visiting the embassy in Juba or send an email to [email protected].
The ministry also said emergencies should be reported immediately to [email protected] and +25420494992.
Kenyan pilots
The travel advisory comes a day after two Kenyan pilots who had been abducted by South Sudan rebels returned home.
Captain Frank Njoroge and his co-pilot Kennedy Shamalla were captured and detained by Akobo local authorities under the control of the rebel force the Sudan People's Liberation Army-In Opposition (SPLA-IO) after their plane crashed in the region.
The two were released one-and-a-half months later, after the rebels were paid $107,743 as compensation for loss of life and property when the plane crashed.
Reporting by Valentine Obara and Kennedy Kimanthi.