Sudanese war planes on Monday launched a fresh bombing raid on Bentiu, capital of the oil-rich South Sudan border state of Unity, killing at least one child, officials said.

"This is a serious escalation, and a violation of the territory of South Sudan... I think it is a clear provocation," Mac Paul, the South's deputy director of military intelligence said.

Five people were killed and six wounded in Sudanese airstrikes on Bentiu, capital of the oil-rich South Sudan border state of Unity, on Saturday.

"Three bombs were released next to Bentiu Bridge, and at the moment one person is confirmed killed. But they did not break the bridge," said Gideon Gatfan, spokesman of the Unity State government.