But the Darfuri rebels, now split into as many as a dozen factions, may themselves be increasing the chaos.

ECONOMIST: Sudan

These rebels were supported by Sudan's government, which was unhappy that Darfuri rebels were using eastern Chad as a base.

BBC: Chad: N'Djamena deaths as 'coup' foiled

He said Darfuri rebels had tried to attack Sudan by coming through South Sudanese territory, and the Sudanese army had responded, but insisted the engagement was inside Sudan.

BBC: South Sudan scraps direct border talks with Khartoum