South Sudanese government forces are approaching the headquarters of rebel forces led by former vice president Riek Machar, a United Nations official says.
David Shearer, the head of the U.N. mission in South Sudan, said thousands of civilians have been displaced in several areas of Upper Nile state as soldiers advance on the rebels' base in the town of Pagak, in the northeast.
Shearer told journalists in Juba Wednesday that there has been heavy fighting between the army, known as the SPLA, and opposition forces, known as the SPLA-IO.
"There has been active military engagement over the past week with heavy fighting around Mathiang, north of Pagak, on July 2," he said. "Reports suggest that the government forces are now in and around Mathiang and approaching the town of Maiwut which is about 25 kilometers northwest of Pagak.”
Both the South Sudan military and the SPLA-IO faction allied to Machar have confirmed the fighting.
Machar is currently believed to be in South Africa. He fled South Sudan last year after a peace agreement crumbled and clashes between government and rebel forces killed some 300 people in the South Sudanese capital, Juba.
Shearer described the situation around Pagak as “extremely worrying,” saying the fighting is worsening the already dire humanitarian situation in the country.
The U.N. Office for the Coordination of Humanitarian Affairs (UNOCHA) said it is deeply concerned about the plight of civilians in areas affected by the clashes.
UNOCHA called on all parties to uphold their responsibilities under international human rights law to protect civilians, and to provide safe, unhindered access for aid agencies trying to provide life-saving assistance.
Shearer condemned the fighting and said it undermines efforts for peace in South Sudan.
"The military advance by the SPLA is not in the spirit of the cease fire declared by the government in May this year when it opened the national dialogue," he said.
A drought coupled with with a three-and-a-half-year conflict has displaced nearly four million South Sudanese and left an estimated six million in need of humanitarian aid.
The war between supporters of President Salva Kiir and backers of former Vice President Machar broke out in December 2013.
Shearer called on the government to improve the security situation, especially in rural areas.
“I certainly agree that the economic output in the country needs to be increased; agriculture has fallen badly behind," he said. "But for that to happen the security situation in rural areas need to be improved dramatically so that people feel safe enough to return to their land to plant their crops. This is particularly the case in the south of the country, which was once the breadbasket of the country.”