South Sudan forces attack rebel stronghold

South Sudan government forces have launched an offensive against a rebel stronghold in the north of the country, the UN said Wednesday.

David Shearer, head of the UN Mission in South Sudan (UNMISS), described "heavy fighting" and an "extremely worrying" situation around the town of Pagak, in Upper Nile region, over the past week, forcing civilians and aid workers to flee.

Speaking in the capital, Juba, Shearer said 5,000 civilians "from the area north of Pagak" have so far crossed the border into Ethiopia to escape the government offensive while "at least 25 aid workers have been forced to relocate from Pagak and surrounding areas due to increased insecurity."

South Sudan's civil war began in December 2013 when President Salva Kiir accused his former deputy, Riek Machar, of plotting a coup. Tens of thousands have been killed and millions forced from their homes in the years since as a series of peace deals have been abandoned.

Machar was forced into exile in South Africa last year but Pagak has remained a military stronghold for his loyalists and the headquarters of his rebellion.

Shearer called for both parties to stop the fighting, insisting there is no military solution to the conflict.