S.Sudan Rebels Warn Government is 'Derailing' Peace Deal

South Sudan's rebels warned Tuesday the government risks a "return to war" by undermining a peace deal as aid agencies reported a fresh upsurge in the 21-month-long conflict.

President Salva Kiir on Friday ordered the number of regional states be nearly tripled from the current 10 to 28, rendering the agreed power sharing formula redundant.

"The objective of this unilateral decision is to arouse tribal sentiments in the people of South Sudan, so that there can be a return to war," said rebel spokesman Mabior Garang.

Garang warned it "would effectively cause the collapse" of the peace deal.

Kiir, who has been fighting to crush a rebellion since December 2013 in which tens of thousands have been killed, the country's economy destroyed and several regions pushed to the brink of famine, signed a peace agreement in August to end the war.

The warning comes amid heavy fighting in northern Unity state, with aid agencies pulling out of the Leer district after gunmen looted their compounds, cutting off aid to starving and sick civilians.

The army and rebels have repeatedly traded blame, accusing each other of breaking the ceasefire, the eighth such agreement to have been signed.

Months of negotiations led to the internationally-brokered deal, including a transitional government and a complex power-sharing formula in which rebels get a share of seats at national and state levels.

The rebels, led by former vice president Riek Machar, also choose the powerful governor posts in the northern battleground states of Unity and Upper Nile, the country's main oil production zones.

The government order says the new reorganization -- which sees the three key states of Unity, Upper Nile and Jonglei split into 10 -- is to "devolve power" to the people.

"This is just another attempt by (some elements in) the Salva Kiir administration to derail the peace agreement," Garang said.

"This is the only thing that can bring our republic back from the abyss."

Both sides are accused of having perpetrated ethnic massacres, recruited and killed children and carried out widespread rape, torture and forced displacement of populations to "cleanse" areas of their opponents.

The International Committee of the Red Cross said Monday it had been forced once again to pull out of its facility in Leer in southern Unity state amid "intense fighting".

The ICRC said "dozens of well-organized armed men entered the compound over the weekend and stole equipment, medical supplies and money."

Medical charity Doctors Without Borders (MSF) said its compound in Leer was raided twice in two days at gunpoint, forcing it to also suspend its operations there for the third time since war broke out in December 2013.

MSF said aid in the area has been "severely limited" since May, when "an upsurge in fighting and violence against civilians displaced hundreds of thousands of people from their homes."

The U.N. Food and Agriculture Organization (FAO) warns of "isolated cases of starvation" in parts of Unity and Upper Nile states -- once the country's main oil producing states, now the epicenter of violence -- which it lists as "one of the world's worst humanitarian and food security situations."

Parts of both states are already classified as being one step short of famine, according to the last technical assessment made in April.