South Sudan's army Tuesday said it killed 28 rebels in armed clashes in South Sudan's Upper Nile State.

"The rebels, loyal to Riek Machar, attacked Jilshal area Tuesday near Sobat River between Al-Nasir and Malakal towns in the Upper Nile State," Philip Aguer, South Sudan's army spokesman, told Xinhua over the phone from Juba, the capital of South Sudan.

"The forces of the Sudan People's Liberation Army (SPLA) pushed back the rebels' attack. The confrontations resulted in the deaths of 28 rebels and the confiscation of weapons and ammunitions," he noted.

He added that the South Sudanese army was still pursuing rebels who fled to the jungle.

On March 5, the Inter-Governmental Authority for Development in Africa said peace talks between the country's warring parties, in order to end over a year of bloodshed in South Sudan, failed due to their remaining differences.

The rebels proposed that the two armed forces in South Sudan should merge after the general elections, scheduled 30 months after signing a peace deal, while Juba rejected the proposition.

The government also refused to accept the rebel movement's demands of 45 percent administrative level positions during a proposed transitional period.

South Sudan plunged into violence in December 2013, when fighting erupted between troops loyal to President Kiir and defectors led by his former deputy Machar.

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

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