The surge in fighting in a conflict that has lasted for four months came amid warnings UN Secretary General Ban Ki -moon that more than one million people at risk of starvation in the war-torn country 's youth .
Peacekeepers from the UN mission in South Sudan ( UNMISS ) are patrolling the capital of the state controlled rebels said they had seen about 35 to 40 bodies along roadsides , mostly in military uniform .
" UNMISS condemned this new feud with the strongest terms , " the mission said in a statement as he called the fighting as a " serious breach " of the ceasefire deal agreed in January .
" The battle will only worsen the already terrible situation , " he added .
Bentiu , a fierce war-torn region , is the first major settlement was retaken in a new attack by the forces of opposition leader Riek Machar , a former vice president .
Conflict in South Sudan have killed thousands of people and forced about a million people fled their homes since fighting occurred on December 15 in the capital Juba before spreading to other states in the oil-rich country .
More than 12 thousand civilians are now sheltering at the United Nations headquarters in Bentiu , protected by peacekeepers , with one person injured in the camp when a bullet from a shootout not far from where it hit the camp .
The insurgents took the city on Tuesday , while the army said it was preparing a counter-attack to take over again .
Insurgents previously occupied Bentiu in December at the start of the conflict , but was expelled from that city a month later .
On Monday , peacekeepers of the United Nations save the 10 employees of the company Safinat Russia when insurgents attacked an oil refinery built in the north of Bentiu . Among them are citizens of Russia , Ukraine and Kenya .
Five people were injured in the fighting.
The battle took place between troops loyal to President Salva Kiir against insurgent forces in favor of Machar who was fired as vice president in 2013 .
( Read: suara cucak ijo )
The conflict has also been included in the current ethnic dimension of President Kiir's Dinka tribe against the forces of the Nuer people , Machar , AFP reported .