Joe Contreras, the acting spokesperson for the UN Mission in South Sudan (UNMISS) said there were around 12,000 people sheltering at the base in Bentiu Thursday, compared to around 7,000 last week.
The number of people seeking refuge at the U.N. base spiked after fighting broke out between government and opposition forces for control of the town.
Anti-government forces said on Monday that they have taken control of Bentiu, which is the capital of South Sudan's second biggest oil-producing state, Unity.
Contreras said the U.N. troops who patrolled Bentiu saw "thousands of internally displaced civilians" at other locations in the town, in particular at the local hospital and at the UN World Food Program compound.
U.N. ‘blue helmets’ who resumed patrols in Bentiu on Wednesday "spotted between 35 and 40 dead bodies along the roadside as they were traveling," Contreras said.
"Most of those corpses they saw were dressed in military uniform. There are some corpses that were dressed in civilian clothes," he said.
The United Nations said in a separate statement, released at U.N. headquarters in New York, that the Sudan People’s Liberation Army (SPLA) headquarters in Bentiu was empty, and shops in the town have been looted.
Army spokesman, Colonel Philip Aguer, said government forces are planning a counterattack on Bentiu.
“The SPLA is coming back, after they withdraw temporarily. Forces of the SPLA are encroaching into Bentiu and anytime, the rebels, they are out of the town,” he said.
Fighting in Upper Nile
Contreras said UNMISS has also had reports of fighting in Wadakona near Renk in Upper Nile state.
Renk is the northernmost town in South Sudan and an important farming and trading crossroads. On the eastern banks of the White Nile River, Renk is also near the oil fields of Upper Nile state, including the largest oil block in the country, Palouge.
Contreras said, however, that fighting has not reached Renk. Upper Nile state information minister Philip Jiben Ogai agreed that the strategic town was peaceful.
But James Gatdet Dak, spokesman for opposition leader Riek Machar, disputed Ogai’s claim, saying fighting was raging in parts of Upper Nile and rebel forces were on the verge of capturing Renk.
“Our forces yesterday repulsed attacks from government troops who attempted to take over the defensive positions of our forces from the western side of the river," he said.
"We responded by shelling the government forces and their positions in Renk town and the shelling has continued today and our forces may take over the town soon,” Gatdet said, adding that the opposition's strategy is to eventually take control of the country's oil resources, the main source of revenue for the government.