NAIROBI, Feb. 21 (Xinhua) -- The Kenyan government on Wednesday issued a travel alert, warning citizens against travelling to several areas in South Sudan affected by inter-ethnic conflict in the last six months.

Kenya's foreign ministry said the travel advisory applies specifically to parts of the Greater Upper Nile Region and in particular Bieh, Latjoor, Akobo, Jonglei, Northern Liech states and parts of Maiwut, Eastern Nile and Boma and Yei River states.

The travel alert cautions all Kenyan nationals living or travelling to South Sudan to move away from and avoid traveling to areas where armed conflicts and inter-ethnic violence have occurred since October 2017.

"Kenyan nationals in other parts of the country are advised to exercise extreme caution as they undertake their daily activities," the ministry said.

The warning comes a day after South Sudan rebels released two Kenyan pilots who were captured in the area of Akobo, Great Upper Nile region, near South Sudan's border with Ethiopia, which is controlled by the rebels.

The two pilots, who had been in captivity since Jan. 7, were released on Monday after their family paid the 108,000 U.S. dollars.

Several people have been held captive during the ongoing four years of conflict including humanitarian workers, oil workers by armed groups.

South Sudan descended into civil strife in 2013 after political disputes between President Salva Kiir and his former deputy Riek 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 resumed fighting in the capital forcing Machar to flee into exile.

The conflict has killed tens of thousands of people and displaced millions that have fled to neighboring countries.