At least 600 people were killed and hundreds others were injured in tribal clashes in Jongolei State in South Sudan.

"Jongolei State witnessed tribal clashes last week which resulted in the killing of more than 600 people and injury of hundreds others," an anonymous security source in the South Sudanese government told Xinhua via phone on Monday.

"The region is now calm after intervention of South Sudan government authorities," the source added.

Southern Sudanese rebel groups in the state, including the rebel militia led by Gen. George Ator who defected from the Sudan People's Liberation Army (SPLA), are active against the South Sudan government.

The United Nations has recently reported bloody tribal clashes in South Sudan, indicating instability in the country only few weeks after its independence.

The UN statistics indicated that around 2,368 people were killed in 330 violent incidents in various parts of the south from the beginning of the year until the end of June.

South Sudan was officially declared independent on July this year in accordance with the result of a referendum on self- determination for southern Sudan, stipulated by the Comprehensive Peace Agreement (CPA), inked between Sudan's ruling National Congress Party (NCP) and the Sudan People's Liberation Movement ( SPLM) in 2005.