The United Nations migration agency has appealed for the immediate release of a volunteer and child who have been missing since the October 27 gun battle in South Sudan that claimed the lives of three agency workers.

According to IOM, the two missing people were also caught in the crossfire between two armed groups in Isebi, Morobo County, in the Central Equatoria region.

The volunteers had been manning an Ebola screening center in the border region between South Sudan and the Democratic Republic of Congo to prevent the spillover of the disease into South Sudan.

The four-year-old child is reported to be the son of one of the IOM workers that were killed.

IOM spokesperson Paul Dillon said that "all possible action" as being taken to secure the release of the two individuals immediately, and that operations had been suspended for the time being in several border areas.

"Obviously, we are there for a reason, to monitor possible flows of Ebola into South Sudan. These individuals in South Sudan as in many other countries are very much on the front line in this response… We have suspended our operations in five of those border areas until we can get clarity on the security situation and the commitment from all actors in that area that the security of our staff in that area will be safeguarded."

South Sudan has been dogged by violence since December 2013, sparked by a feud between President Salva Kiir and Riek Machar, his former deputy president.

Talks are ongoing to put the country back on a peace path and the formation of a transitional unity government that will include the warring factions.

(Information obtained from UN)