South Sudan's claims of coup attempt prompts Western concerns

"[I am] deeply concerned about incidents of fighting in Juba, South Sudan," he said in a statement published through his official Twitter account. "I call on all sides to stop [fighting] and appeal for calm."

The independent South Sudan News Agency reports President Salva Kiir was characterizing the security incident as an attempted coup launched by his political rivals. The president appeared on state television in his military uniform, saying forces loyal to former Vice President Riek Machar tried to topple his administration.

Machar was dismissed during a Cabinet reshuffle in July. The South Sudanese news agency said multilateral political talks broke down last week when Kiir's rivals accused him of short-changing democracy.

U.S. State Department spokeswoman Marie Harf said during a Monday press briefing the U.S. government was monitoring the situation closely.

Washington helped broker the peace agreement with Sudan in 2005, which paved the way for a South Sudanese referendum for independence in 2011.

The U.S. Embassy in Juba said Monday the security situation had calmed down but stressed traveling through the capital was still considered unsafe.