The United Nations is calling for a halt to violence in South Sudan's Jonglei state, where tribal clashes have killed hundreds of people since Thursday.

The U.N. mission in South Sudan said Monday that the fighting has “reportedly resulted” in 600 deaths and injuries to at least 750.

South Sudanese officials say the fighting stems from a cattle dispute between the Murle tribe and the Lou-Nuer tribe. The two tribes often clash over cattle and land.

Hilda Johnson, a special representative for U.N. Secretary-General Ban Ki-moon, said the cycle of violence must stop, and called for reconciliation efforts. She said the U.N. is ready and willing to support a local peace process.

South Sudan became the world's newest independent country last month, after voting to split from the north.

The new country has been plagued with tribal violence and clashes between the government and rebel militias.

The government has urged South Sudanese to work together, saying the country has the potential to become the breadbasket of eastern Africa.