Uganda has deployed an unknown number of troops to South Sudan in a bid to protect the fragile government of President Salva Kiir as a tense rivalry with his deputy threatens a return to civil war in the east African nation.

Uganda has deployed special forces in South Sudan's capital Juba to "secure it", Uganda's military chief said on Tuesday, but South Sudan's information minister denied the presence of troops, as tensions between South Sudan's president and first vice president stoke fears of a return to war.

The leadership of the United People’s Alliance (UPA) has condemned the decision by the Government of South Sudan to invite the Uganda People’s Defence Forces (UPDF) to South Sudan amid tensions and conflicts in Upper Nile, Western Bhar Ghazal and Western Equatoria states.