South Sudan's army has suffered casualties in days of intensive fighting in Upper Nile State and has evacuated dozens of wounded soldiers by air to Juba for medical treatment, according to an eyewitness.

The army (SPLA-Juba) has been battling forces of a previously allied commander General Johnson Olony and elements of the SPLA-IO in Malakal and other areas of Upper Nile State. The rebel SPLA-IO has claimed control over Malakal and government troops retreated northward to oil-producing areas still under their control including Akoka, Melut and Paloich.

A source in Juba said that wounded SPLA-Juba soldiers arrived at the Juba International Airport on Sunday at 5 p.m. from the Upper Nile front via Paloich airstrip in Upper Nile State, which is located north of the frontline at the heart of the oil-producing area.

Seen by an eyewitness, the wounded soldiers were brought toward the military hospital at Giyada. Althought the witness was unable to count precisely the number of wounded he said that he saw one bus carrying wounded soldiers, an open Land Cruiser full of wounded soldiers and an army ambulance full of wounded soldiers.

File photo: Wounded soldiers lie in bed at the general military hospital Juba, 28 December 2013. (Reuters/James Akena)