S. Sudan seizes full control of Upper Nile State

South Sudan military has fully controlled the oil-rich Upper Nile State after three-week heavy fighting against rebels, President Salva Kiir said in a statement on Friday.

"The Upper Nile has been freed from the rebels and from Johnson Olony (an army general who recently defected and joined the rebels)," said the statement.

"Our citizens and our oilfields are under protection of the army loyal to the South Sudan government," the statement said.

In the statement, the president also pledged to do everything to restore calm in the state.

The South Sudan rebels recently announced that they captured an oil refinery near Paloch oil field in Upper Nile State, and demanded oil firms suspend their operation and evacuate the staff.

On Wednesday, the rebels led by former vice President Riek Machar also said their forces have controlled great parts of Foluj oilfield, the main oil-producing field in Upper Nile State.

Over the past week, the rebels have been launching wide range attacks on Malakal, capital city of Upper Nile State, which flared battles between rebels and government forces in the area.

South Sudan, which became independent in 2011, plunged into violence in December 2013, when fighting erupted between troops loyal to Salva Kiir and defectors headed by his former deputy Riek Machar.

The conflict soon turned into an all-out war, with violence taking on an ethnic dimension that pitted the president's Dinka tribe against Machar's Nuer ethnic group.

The clashes have left thousands of South Sudanese dead and forced around 1.9 million people to flee their homes. Endit