South Sudan: Why are the stakes so high for President Salva Kiir and his deputy Riek Machar?

The arrest of Machar last week was seen by some observers as the spark that could reignite the civil war that the rivals fought between 2013 and 2018 that killed some 400,000 people.

But others argue that the situation has changed considerably since the last conflict with new political struggles now centre-stage.

Succession

Analysts say Kiir, 73, is struggling with health issues and has been seeking to ensure his succession and sideline Machar politically.

"The succession is the major issue in South Sudan, with President Kiir not in good health and people within his party and government trying to take over," a Juba-based humanitarian told AFP, requesting anonymity for security reasons.

Since February, more than 20 of Machar's political and military allies have been arrested, some held incommunicado.