This is a story for which I have no confirmation, but Eric Reeves has been following Sudan for many years and is highly respected.
A Coup in the Making in South Sudan – led by Riek Machar
Eric Reeves | July 10, 2016 (7pm EDT)
A highly reliable source—currently in the region and with extensive experience in South Sudan over many years—reports from Addis Ababa this evening that a coup in Juba is being led by Riek Machar, First Vice-President of the Government of South Sudan. The military side of the campaign is being led by Sudan People’s Liberation Army-In Opposition (SPLA-IO) Commander James Koang Chuol, who has today been communicating with Peter Gadet, another SPLA commander, with a notorious record for brutality (as well as changing sides in the midst of conflict). My source also informs me that Riek Machar has asked the Khartoum regime for more weapons and military assistance (see leaked minutes of August 31, 2014 meeting of senior Khartoum regime military and security officials, during which such military assistance to Riek Machar and the SPLA-IO is discussed at length, with clear consensus on the advisability of going ahead the plan | http://sudanreeves.org/2014/09/29/arabic-original-hand-written-english-translation-of-31-august-2014-meeting/).
Based on intercepted communications, a full-scale assault by General James Koang Chuol is expected to begin early tomorrow. This will be in addition to the extremely intense fighting that descended upon Juba again today (Sunday, July 10, 2016).
Humanitarians from some non-African countries have begun to be evacuated; more are likely to be evacuated in the very near future, and total humanitarian evacuation now seems a possibility.
The stakes for the people of South Sudan could not be higher. The international community must urgently reinforce and re-configure the UN Mission in South Sudan (UNMISS) to function as a civilian protection force, including protection of all humanitarian workers.
As a great as the present catastrophe in South Sudan is, it has the potential to become much, much worse.
Eric Reeves, Senior Fellow at Harvard University’s François-Xavier Bagnoud Center for Health and Human Rights